Windows 8 Preview is able for everyone to download and try. I got it running on my laptop, and here's my comments.
It's going to be quite a change. No longer is the Start button at the bottom, but the Start Screen (as in Windows Phone 7).
Full-screen Metro Internet Explorer 10. Note - you are not allow to have toolbars and plugins (that includes Flash). (Microsoft calls it "addon-free experience".) But this thing is quite fast, considering that I am running Win8 with a 4-year old laptop.
To see the apps you are running concurrently, move the mouse to the left edge of the screen. [Note in this screen, I'm in "Desktop" - the good-old familar Windows screen]
It's all about apps! The Win8 App Store ("Store" - the very first tile) is where you get Metro-styled apps. All Metro apps must come from "Store", and maybe run on both x86, x64 and ARM platforms. [Note: for the new class of Windows devices running ARM CPUs, you cannot run legacy Intel Windows apps on them - so be aware of this when you shop for new Windows 8 devices.]
Weather app. Note that the background matches the weather of the City you are viewing.
Picture Gallery. You can integrate your Facebook and Flickr accounts, along with your local files, and have it all displayed in one integrated view. For testing though, I did not have that setup (nor would I want to plaster my pictures on the forums here anyways. 
App updates. If you have a smartphone with Windows Phone 7, this probably looks familiar to you.
To get to the settings of the app, hover the mouse to the top right corner, a column of icons will appear, then click on "Settings" (with an icon that looks like a gear). PC settings may also be access in that panel (including shutting down the PC).
If you click "More PC Settings" in the picture above, this is what you'll get. [Note - these are only the basic settings. For the more advanced settings, you have to use the good old Control Panel from the Desktop.
That's all for now. Time for some zzzz.....
One more thing...
To learn more about Windows 8, here's the link on Microsoft's site:
http://windows.microsoft.com/en-US/windows-8/consu
