Well, one of the problems is that you can't change the MIDI output for your sound card (MS wavesynth suck big time, I want to use xg or Timidity driver to load soundfonts), even midi output interface didn't change from xp, I don't know why it's hidden or something, last time, I had to download control panel tool to change it, instead of changing registry values, besides some discontinued programs used to work on xp but not vista (no patches..
), some WDM drivers worked on xp don't work on vista (wdm drivers should work according to it's definition, see wiki)
heck, you can't even run ms-dos applications in full screen (vista home edition, dunno bout others)..