I've not tested MediaEngine with vista. Personally I don't like vista. I know this may sound backwards, but Vista is just "too much" for a car environment. I'm working on a XPE setup (XP stripped down) and its still *almost* too much.
The front end apps available are not going to take advantage of vista's new "stuff". You might be better off using XP for now. You probably won't have hardly any issues.