Both ASCII Gearheads work pretty well on Vista, for me. GH2 has this thing where you can't really resize the window (That I've been able to figure out. Royal pain, that.), and GH1's a pain to do that at all... and there's some issues with doing so, if you're not careful. Screen buffer must match what it says in the .cfg or things go wonky.
Shouldn't be a problem if you're just putting window in, though. O'course, the window flag doesn't even do anything for the non-SDL build, which runs windowed naturally, so...
That's the only issues... that I know of, with the ASCII version. Everything else is as mistah Munoz says. Don't play the SDL version personally, so I've no clue if that'll run smoothly or not, but Vista's a tricky beast, so your mileage may vary, et al. Good luck, heh.