Ive been following the development of 7 quite a bit actually and it seems like they are going to really think this one through because the core technologies and ease of use are getting a massive overhaul. I stayed clear of Vista because of the backlash it got, having used it myself for a couple of months I really think its terrible. Simple things like finding display settings from the desktop is a pain (they have now fixed that with 7).
As for the UI of 7 it still looks like any BETA would (like Vista with a few different buttons) but I hope it will drastically change for public release.
One thing that does bug me however, the new start bar default button style looks like they tried to copy OSX's dock and failed massively. Seriously it looks like something from the 90's or windows live tools rather than a sleek operating system, luckly you can switch it back to a more traditional style. Either make it 3D or dont bother with it MS!
Also they really need to do a time machine clone, yes it has shadow volume copy but it needs an easy visual UI for it to be really marketable.
I would download the public beta it if I had a spare computer and HDD to hand but I don't so I guess I will wait to see how everything goes till full release.
Theres lots of info on Paul Thurrott's site (yes he is a total MS Fanboy) but thats where to go for 7.
Robin.