Well I am definately underwhelmed at the moment. Sure it looks nice, but so did XP. I was expecting a host of revolutionary features, but at the moment it just looks like a slightly modified XP.
Hopefully they are just keeping the real big features under wraps until they are closer to ship date.
The "3D Desktop" is kind of pointless, unless it does a lot more than the alt-tab switching. Thats just an existing feature skewed into the 3rd dimension. It doesnt add any extra functionality at all. Just looks like a gimmick to me...