I've tried out the Windows 8 Consumer Preview. So far it's okay. You can tell it was obviously made for tablet computers though, but it runs fine on a desktop. To access the start menu you have to press the Windows logo key on your keyboard as the start menu button has been removed from the desktop. And as I'm sure everyone knows, the start menu is now full screen with tiles (which I don't mind, I think it looks nice).
Windows 8 also connects with your Windows Live ID (like, for the user you enter your Windows Live ID (although the option to make a local user still exists)). I haven't connected my WLID but I've heard that it connects all your data (including credit card info). Windows 8 also connects to Xbox Live (I've heard rumours of it being able to play Xbox360 games but I don't know if that's possible yet).
Microsoft has also added their own app store to download metro apps from (you can still download anything from the Internet, however, if it's not compatible with the metro UI it runs the way you're used to it (in a window on the desktop)). If it's a metro app it runs full screen in the start menu.
Also, if you move the cursor to either side of the screen (at the very top or bottom) a menu pops up (on the left is open metro apps; on the right is settings and also the power button to shut down/sleep/restart etc).
They've even gone ahead and made the BSoD look nicer.
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Overall it's fine, it just takes some getting used to but once you're used to it you'll be fine. I personally wont buy it however, unless it can either play Xbox360 games or I need to purchase a new Windows 7 key (currently I use Windows for everything even though I prefer Linux
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(slowly moving to Linux however, but for gaming I'll be sticking with Windows for awhile (although games are starting to show up on Linux))).
What I plan to do eventually is run Ubuntu 12.04 (when it's out of beta (which is in 5 days)) and then virtualize Windows 7 or 8 on top of Ubuntu for gaming (hopefully it wont effect performance TOO much
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).