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.
i have got media engine to work with windows vista, you have to remove the permissions from vista (the annoying allow and deny boxes in vista). to do this you need to go into control panel then goto user accounts icon and click it. then go to turn user account control on or off and untick use user account control (UAC) to help protect your computer and press ok this will require you to restart the computer but once this is done you need to reset the media engine db_update.
i can get media engine to work fine except the videos are not working.
the added bounus of removing the permisions is that now it doesnt ask every time you want to open programs.