NOTE: This article is in the process of being completely revised as we play around with the new Release Preview - keep checking back for more. 
The Windows 8 Release Preview (here's the Windows 8 download) has now been released.
Although the Windows 8 Release Preview is far from finished (with more changes to the desktop user interface still to come before RTM at the end of July), this is an operating system that has matured significantly since the Consumer Preview release in February.
Metro is here to stay, but between improvements to the way you switch apps and open Charms with the mouse and trackpad; significant improvements to the Mail, Calendar, People and Photos apps; the addition of Flash to Metro-style IE; more Metro apps to try out; more attractive live tiles and a better range of colours for personalising the Start screen.
You may not find that as disturbing as you think, especially when more notebooks support the full set of trackpad gestures.
There are improvements on the desktop as well, from minor interface changes in Explorer and improved multimonitor support to privacy and navigation improvements in Internet Explorer. Performance and responsiveness are improved from the already speedy Consumer Preview, rough edges are getting their final polish and the big picture of Windows 8 is coming together. So what does that big picture look like?

Running the Windows 8 Release Preview

First of all, it's worth noting that the Release Preview is only for x86/64 PCs; there isn't an ARM version that you can download and try out, since there aren't any ARM devices that will run it.
That's because of the extremely custom way that ARM devices are built, where not even the way to control a physical button is standard. Microsoft isn't supporting tablets built to run Android or WebOS, either.
Much of what we're seeing in the Review Preview will be the same on Windows RT) systems. Most features - from the Metro user interface to the touch gestures, to the Windows desktop and built-in Windows tools such as Explorer and Task Manager - will be practically the same.
Windows 8 Release Preview: Start apps
Microsoft has even confirmed it will offer Flash functionality for IE on Windows RT (at least on what it calls the "initial delivery of Windows RT PCs"). But until we see it in action, we don't know what Windows RT performance and battery life will be like.
Windows 8 Release Preview YouTube
Release Preview doesn't include the desktop Office apps that will be bundled with Windows RT either - and of course it runs all the x86 desktop apps that won't work on RT.
When you download the Release Preview, installing is as simple as for Consumer Preview. You can start the installation directly from the web page, instead of having to download an ISO file and burn that to an optical disc. You can still burn an ISO if you want, and the installer can also create a bootable USB stick so you can download Release Preview once and install it on multiple machines.
As with Consumer Preview, how much of a previous Windows system you can keep when you install Release Preview depends on which version you're upgrading from; upgrade from Windows 7 and you can keep programs, Windows settings, user accounts and files, upgrade from XP and you only get accounts and files.
Unlike Consumer Preview, you can't upgrade from any of the previous Windows 8 preview releases; what you get is a clean installation with all your files moved into a WINDOWS.OLD folder where you can retrieve them.
If you can copy the files to an external drive it's much faster to do a clean install (which took ten minutes to get to the personalisation screen on our test PCs) than an upgrade from Consumer Preview (which took 30 minutes on all our test PCs).
Once you've typed in the product key and agreed to the licence and your PC has rebooted a couple of times, the Personalize settings are the first screen you see. You still only get six abstract designs to choose from but there are now 25 colour schemes to choose between, and the on-screen slider shows both the colours in each scheme.
Windows 8 Release Preview setup
Some of these are extremely bright; the vivid pink background is quite the eye-opener. We'll also miss the Metro-style beta fish design which is gone from the boot loader and the desktop tile, replaced by the word Windows and your chosen desktop background. There are also new images you can use for the Lock screen.
Windows 8 Release Preview: Settings
The touch and mouse gestures don't change dramatically from Consumer Preview; they just work better. Swipe from the right edge of the screen and you still get the charm bar; Search, Share, Start, Devices and Settings. You can do the same thing by leaving your mouse pointer in the top or bottom right corner; first the charms appear as white outlines, then if you don't move your mouse they disappear.
Windows 8 Release Preview Share
Windows assumes you didn't want to trigger them, since you might be moving the mouse to scroll or closing a window at the side of the screen instead. If you are, you don't have to wait for the charms to vanish to do so. Move the mouse towards the charms and the black bar and charm titles draw in on screen.
Small, subtle changes in the design help to make more sense of the Metro interface (but also make us wonder whether internal Microsoft testers who didn't need this kind of help were very smart or very frustrated - or whether the look of the Metro interface is relatively recent).
The hot corners for charms and the app switcher bar have been tweaked so they're easier to select on purpose and harder to trigger by accident; it's like the difference between a drawer that keeps sticking and one fits properly and opens and shuts smoothly. Suddenly using Metro with a mouse feels less haphazard and clumsy.
Swiping the app switcher in from the left edge of a touch screen with your finger is smoother and less fiddly as well. Dragging Metro apps to the bottom of the screen to close them is far more responsive; almost too responsive sometimes. Twice we accidentally closed the picture password setup half way through by dragging down too far with a gesture.
The labels under each app thumbnail (which look so much like TechRadar's new caption style that we're flattered) make the app switcher clearer and the way the Start screen thumbnail pops up as soon as you drop the mouse into the lower left corner of the screen makes it feel more like a rectangular Start button than an unwelcome reminder of Metro.
The Settings charms for Metro apps get labels as well. Instead of saying Start or Mail at the top, the bar is now labelled Settings, with the app name greyed out at the top. are clearer; the options for the Start screen settings are now Tiles and Help rather than Settings and Help and seeing the word Screen makes it more obvious that this is where you change screen brightness than a number and a sun-ray brightness icon.
Windows 8 Release Preview: Settings in Metro
The Keyboard icon is replaced by the name of the keyboard layout you're using. If there's any choice between cute but confusing and obvious, Release Preview picks obvious.
Others options here have extra options. The Volume bar gets a mute button as well as a slider and instead of turning notifications on or off, you can hide them for one, three or eight hours while you get some work done. This will become more important if you get a lot of mail or calendar alerts to deal with, although they pop up in the top right corner of the screen where they're too not in the way.
It's handy that the first time you put a USB stick in, you can choose whether to open Explorer or do something else, and that will happen automatically next time you insert it. But it could easily get annoying with too many toasts (as Microsoft calls them) popping up.

Search and share

With more apps installed, the other Charms make more sense too. Far more apps use the Search contract, so they show up as options when you search. Search is still context sensitive; if you're in IE when you choose it, you get results from Bing first, but you can switch to results from other apps by choosing their icon.
Windows 8 Release Preview: Bing
Similarly, more apps let you share, and share is about more than sending tweets or emailing links to Web pages; you pick Share to send a photo from a viewer to an image editing app or to print it. This could be one of the more exciting tools in Metro and we're starting to see apps take advantage of it.

Tiles and typing

Working with tiles is a little faster and more responsive but otherwise much the same. The Semantic zoom feature still lets you pinch to shrink the tiles on the Start screen to tiny thumbnails so you can see everything at once or move an entire group.
Select a group and drag it down to get the option of naming it. This is also the view you get when you drag a tile you're moving to the bottom of the screen, which makes it easier to move an item a long way across the screen without disturbing the arrangement of all your tiles and groups. As you drag a tile between two groups, when you position it between them a vertical grey bar appears to show that you're creating a new group to put it in.
When you use a mouse, just sliding from side to side scrolls the Start screen back and forth just as in Consumer Preview, but the button on the scrollbar that turns on Semantic Zoom is now a more obvious, more Metro-style minus sign.
The on-screen keyboard is also much the same as in Consumer Preview, including a handwriting panel, a large touch keyboard with predictive text and spelling corrections, a full keyboard with function keys and a thumb keyboard layout with has the alphabet split between the two sides of the screen where it's all in reach of your thumbs, and a numeric keyboard in the middle to make it faster to type passwords (or indeed, numbers). You can dock or resize any keyboard.
As with Consumer Preview, having your email, photos, appointments and friends pinned to the Start screen livens it up considerably. The live tiles paint in far more quickly when you first set up your account in Release Preview and they're more colourful. There are also more apps in the Windows Store to try out.
Windows 8 Release Preview Apps
Many of the preview apps from Consumer Preview have been significantly updated; they're faster, far more reliable and have more features too. Existing features work better; Bing Maps would show you traffic data in Consumer Preview but it loads far more quickly in Release Preview.
Windows 8 Release Preview Bing Maps
Windows 8 Release Preview Bing Daily
Connecting to cloud services where you store photos, like Flickr and SkyDrive was slow in Consumer Preview and sometimes took a couple of attempts; in Release Preview the services and albums appear almost instantly - including a link to photos you have on other PCs that are running the SkyDrive app.
Windows 8 Release Preview: Pictures
You can swipe through images, zoom out to see thumbnails, play a slide show or pick an image for the Lock screen, simply and elegantly.
Windows 8 Release Preview: SkyDrive
The People hub still combines the address books for all the services you link Windows to, through your Live account or by adding specific accounts for email and calendar and it still takes a lot of space to show contacts and updates but it's far faster and more responsive.
Windows 8 Release Preview: People
Pinch zoom and you go straight from tiles with photos on to an alphabet you can navigate with; you can also just stat typing a name to jump to it. The 'Me' view is more useful, gathering notifications and replies as well as a list of your own status updates.
The Messaging app gets a bright purple colour scheme but no other real changes; it makes good use of the screen to show you multiple conversations on Facebook and Windows Live, with details about your contacts so you can see what they're talking about on other services. You can also send group messages, but it's just text chat; no voice or video yet.
Windows 8 Release Preview Messaging
Mail still isn't an Outlook replacement; you don't get categories, you can't flag messages for follow up or mark them as spam, there's still no threading or conversation view and it still only works with Hotmail, Gmail and Exchange accounts.
Windows 8 Release Preview: Mail
But you can now see your tree of folders without having to swipe back and forth between panes, you can tap on attachments in a message, download them and tap to open them without delving into the app bar. You can also pin any folder to the Start menu as a secondary tile to see message subjects as they arrive.
Windows 8 Release Preview: mail
Windows 8 Release Preview Security
The Calendar still aggregates calendar feeds from multiple accounts and gives you two-day, week and month views, but you can now turn individual calendars on and off and pick the colours the way you can on Windows Phone. And you get on-screen notifications for meetings and alerts that you've set, making it considerably more useful.
Windows 8 Release Preview Calendar
Other apps haven't changed as much. The Metro SkyDrive app still doesn't sync files the way the desktop SkyDrive app does; it's for viewing files when you're online in a clean and simple interface with tiles for folders and thumbnails for images. You can now switch between thumbnails and detail view in folders and you can delete files with the Manage button.
It's a great way to work with your online files; documents on your SkyDrive still open in the Office web apps in Metro IE rather than directly in the SkyDrive app but PDFs open in Windows Reader, which remains an excellent and simple PDF tool. Large files open quickly and scrolling through documents is equally fast.
Windows 8 Release Preview IE10
Windows 8 Release Preview IE10
There are no confusing toolbars floating over the page; you can pinch to zoom in and out or double tap to zoom into a page, and the commands on the app bar enable you to search, switch views, rotate a page or see what you have permission to do with a password-protected PDF. This is far more pleasant to use than Acrobat Reader - and noticeably faster. The only change in Release Preview is the ability to close the PDF file you're reading.
The Finance and Weather apps are still good examples of what a rich, content-filled Metro app can look like; the new News, Sports and Travel apps are similar. You can browse through stories or pick a topic, team or destination and pin it to the Start screen to see updates.
The Zune branding in the Music and Video apps has been relegated to the account details in Settings (the Xbox Live ads that have appeared in the catalogues are far more noticeable) and both have been redesigned.
Windows 8 Release Preview Music
Your own music and videos are now tucked away on the left of the screen, out of sight, with no indication that you need to swipe in that direction. The music and video player will still be very familiar to Zune HD and Windows Phone users but they no longer take over the whole screen, making it easier to find the next track you want to add to the playlist.
Windows 8 Release Preview Music
Windows 8 Release Preview
The Xbox Controller still shows what you can do on the Xbox screen and you can touch areas directly, so instead of looking on the Xbox screen to see that the B button means back, you get a back button to press. That's less fiddly on a large screen than the way the Windows Phone app turns your PC into a replica of the Xbox controller.
Windows 8 Release Preview Xbox live games
This is going to work best with tablets, but on any PC the option to pick a movie or TV show from the Video app and play it directly on your Xbox is a great way of doing things. You get to search the catalogue using a keyboard, so it's easy to find the show you want and then sit back and watch it on the big screen, where it looks good.
The Xbox Live Games app still looks reminiscent of the Xbox and Windows Phone but with a greyer colour scheme. Again to find your avatar and those of your Xbox Live friends you have to swipe over to the left and there's no clue to suggest it. You can see your achievements on phone and Xbox games, but none of the games in the Windows Store have Xbox Live integration yet so all you see are adverts for Xbox games.
The Store itself has some changes; the most useful is the Your apps option on the app bar, which shows you a list of all the apps you've downloaded previously, which you can sort by whether they're currently installed and filter to show which apps you have on which PC. The Store will also start to include desktop apps from this week.
Windows 8 Release Preview Your apps
Windows 8 Release Preview Your apps
 Popular and polished as Windows 7 is, there are irritations like Explorer jumping the view back as you explore deep nested folders, and the intrusive language toolbar. The Windows 8 desktop addresses all of our complaints, but it also takes away the familiar Start menu. Does that make it hard to use, with or without touch?
Windows 8 Release Preview
There's no denying that this is a different way of working; press the Start key on your keyboard and yes, you get the Metro Start screen.
But if you roll your mouse into the familiar left-hand corner you get a thumbnail of the Start screen and you can roll up to get the list of Metro apps running as thumbnails (or use Win+Tab), so you can jump directly to another running app without the disruption of the full-screen tile layout. Or you can use Alt+Tab to switch between all running apps, Metro or desktop.
If there's a Metro app pinned at the side - which you can easily do by dragging the thumbnail that appears when you mouse into the top left corner - Alt+Tab respects that and switches the app in the pane you were working in last.
Windows plus the '.' key swaps apps between the different window positions on screen at top speed.
There are far more ways of switching between apps than before, so you can pick the ones you prefer and ignore the others.
If you want quick access to desktop tools without going back to the Start screen at all, right-click in the very farthest point of the left-hand corner to get a handy menu with just about everything you could want: Search, Run, open Explorer, Task Manager or Control Panel, run tools such as Disk Management, Device Manager, Event Viewer or Power Options.
Windows 8 Release Preview Control Panel
You can also jump to the control panel settings for Network Connections, System or Programs and Features and open the command prompt, as admin or a normal user. Windows+X opens this and you can navigate it with the keyboard, so if you want the Event Viewer in a hurry and you haven't already pinned it to the task bar, press Windows+X+E.
And there's still Windows+R to run any app directly. Frankly, this addresses any complaints we had about losing the old Start menu; there are neat and efficient ways to get to everything you want in the desktop without ever taking your hands off the desktop or having to see Metro.
The charm bar works far better in the desktop in Consumer Preview as well. Throw your mouse over in the corner and the charms ghost in, in case you didn't really want them. Like the hints of app thumbnails in the switching pane, this hints at what you can do without getting in the way of working with windows and controls on the edge of the screen.
Start is there for systems with no hardware Windows button, Search is there for consistency but Devices and Settings both give you the desktop tools rather than the Metro ones. The Settings pane has icons for network connections, volume, screen brightness, switching language, turning popup notifications on and off plus Sleep, Shutdown and Restart.
There are links to Help, System Information, personalising the desktop and the full control panel at the top; if you want the friendly Metro PC settings, that's a link at the bottom.
Windows 8 Release Preview
Compared to the jumble of ways you could navigate to key tools, control panels and utilities in Windows 7, this is a streamlined and efficient interface - and again, you never leave the desktop unless you want to.
That irritating language bar? Replaced by an option to switch language from the Settings charm (or you can use Windows+spacebar to flip between installed languages).
There are a couple of points where Windows 8 sacrifices convenience for improved security. If you have two accounts on one PC, even if they're both signed in, you have to unlock the PC with the account that was in use last.
Unlike Windows 7, there's no way to choose which of the accounts to log in with from the lock screen. This will be unpopular in multi-user households.
Also, when you log into a Wi-Fi access point, instead of the password dialog showing what you type by default, Windows 8 hides your wireless password and only reveals what you've typed when you press and hold the cryptic icon next to the field (which might or might not be an eye for visibility).
With touch, the desktop is a bit of a hybrid. You can use gestures at the sides of the screen for task switching and working with charms, and you can swipe to switch to Metro apps. You can even swipe down from the top of the screen and drag the thumbnail off screen to close the desktop like any other Metro app. You can also touch anything you'd click with a mouse.
This works extremely well with ribbon controls (and makes it initially annoying that Microsoft has bowed to complaints from people who've never used a ribbon interface with touch and made it minimised by default).
Windows 8 Release Preview
Smaller controls work surprisingly well too, because Microsoft has used machine learning to predict where you're really trying to tap for the desktop and built-in apps. We found this made accurately selecting tiny drop-downs and menu items in Office and third party applications easy (on a Samsung Slate 7, which has a good touchscreen to start with).
It can get fiddly; multi-selecting files in Explorer didn't always give us all the files we wanted, but Windows 8 does an excellent job of making an interface that was never designed for touch work with your fingers