yip, I'd make sure you understand that the software you're wanting to run actually works on vista. I've had to live with significan't changes in the interface which I haven't allways liked. From a Notebook perspective, switching Aero off when going on to batery, etc can be a bit tedious.
Mostly though, some software just does not work, especially anything that ties into driver access like screen capturing software, etc. Most of my customers are demanding to stay on XP for a while until SP1 or until all other choices are removed.
It's the old Windows 2000 debate all over again ;)