I run Vista 64bit and tremulous. A bit of messing around was required, but nothing a streetwise unprofessional cannot do.
It seems my gamma is a bit broken though, i cannot change it in the console, and I have to use the bar, which is always at max, so i have to slide it down again before I slide it up, which makes it bright as normal.
But these are very minor problems, and can probably be solved permanently without much bother.
All in all, it was more painless than i excepted it to be.