Hi there. I've been running ufo:ai on vista too, but I've been running RC6, not the latest beta. I don't remember any specific install issues, but I've installed quite a bit of software and lots of issues have come up. If there was something amiss, I fixed it without a big hassle.
I'm going to grab up the latest beta and try it out for a bit. I've been experiencing lock ups of my video driver (but vista resets it w/o crashing) but that probably has more to do with this laptop's video arrangement. Anyways, I think this game is a great piece of work. Improving on a really excellent game is hard to do, but it's obvious you'll have succeeded as soon as you're 'finished' (the quotes are there cause I know how these open source things go, you're never fully finished until it has every appropriate feature imagined).
So thanks, and though I'm not a strong programmer, I'll do what I can to chip in.