I've seen a few videos now crop up on Windows 8. There is no beta or release candidate available so if you want to learn more about Windows 8 you've got to rely on the few videos floating around. This video is from the D9 conference in Ranchos Palos Verde.
You can see from the video it looks like Windows 8 is really Windows Phone 7 + Windows 7. You get the tile overlay of Windows Phone 7 in place of the Windows 7's sidebar and start screen and you can also switch to the Windows 7 interface for regular use. The touch gestures look pretty nice and resemble the PlayBook.
It seems weird Microsoft would combine all these features instead of separating the desktop and tablet OS's but I guess this will make sure Windows stays relevant in an increasingly touch / mobile world.