Not sure why, but I really like the translucent window frames. Tabbed browser windows are nice, but there are lots of ways to get them.
In most other ways I find the UI changes annoying, eg. for a dial-up user it now takes a lot more clicks to get to the "status" display to find out how the ol' dial-up connection is working. That would be fine if other common functions took *less* clicks but I'm not seeing that (other than being relentlessly herded towards other Microsoft net resources).
The disk partitioning tools seem to be more capable than XPs -- or maybe I just didn't know how to use XP. Shrinking a huge C: drive to make room for dual-booting Linux is now much easier
I upgraded because I had an XP license, was buying a new PC, and figured it made more sense to get a Vista license than another XP license. I also figure there have to be some good things hidden in there -- I just have to find 'em.
I do really like the translucent window frames. Did I mention that ?