I actually tried it out a few weeks ago, from the Consumer Review version... I'm not too impressed. Maybe for a Tablet, which I'll hopefully be getting one, I'd be a lot more pleased
But as a desktop solution, it seems more like a visual and UI update then anything. It runs programs a *wee* bit faster, but not enough that it makes much difference.
Not to mention, the fact that the main screen isn't the desktop, and that you have to navigate back to it often, is very much a turn off. Especially since I have yet to find a simple way to organize the "Main menu" screen. And, I was having issue synchronizing my Windows Live account to it, which also made a lot of apps either not work, or just have no point.
If they release it with some sort of way to have a "Desktop optimized" UI, then that'd be great. But really, this seems to be only a good choice for Tablets/Tablet Computers.