My experience with Vista so far:
Daemon Tools won't work.
Firefox's default theme seems to make huge scrollbars.
The default security settings are annoying as hell.
Microsoft didn't add ANY good features for us dual monitor users. Waiting for Ultramon3 to fix the problem, as usual.
My printer drivers aren't available for Vista. (They stop at R320, I have R340 >.>)
My scanner drivers aren't available for Vista.
My TV tuner drivers aren't available for Vista.
Gadgets which update every second or more (CPU/MEM meter, clock with second hand, uptime, etc) will increase your CPU usage quite a bit. (15% continuous with all 3 on)
Some programs can't use Aero, so Windows temporarily reverts to non-aero which besides looking ugly as sin, also takes the PC a good minute or two to switch in and out.
Creative's drivers leave room for improvement (They work, but it's missing some of the surround settings and such that I used for music). Thankfully, my speakers have ways of compensating