Just installed Release Candidate 1 (RC1) of Windows Vista and I have to say, I'm impressed.
First of all, it installed easily. I didn't have to backup my data, all of my programs are working, and I had no glitches (save 1 small one).
The interface is SIGNIFICANTLY better. I'm getting the message that the folks back in Redmond took usability to heart as a key issue for both Vista and Office.
Everything is just a lot smoother. I think it's easier to find things and the "feel" is quite improved.
I've only had it up for about 2 hours, but so far, so good.