I have also heard something about Vista having to phone home occasionally to be authenticated or it shuts itself down. I haven't seen this myself so it is only hearsay but having seen M$ in action before, it makes me take a more cautious approach.
Aero sucks down RAM bigtime and the word in the Cinema forum is XPPro 64 runs Cinema faster than Vista.

Pass no temptation lightly by, for one never knows when it may pass again!