I haven't heard great things about Vista. In fact, most of what I have heard has been negative, Bugs, slower game speeds, etc. Eventually that will all be worked out but today, which OS would you use? I have used XP Pro for a few years now and like it. Should I consider the 64 bit version of that for a new computer? Does 64 bit even mean anything right now?
I would suggest win xp prof, and maybe a upgrade couple to use after they fix all the bugs. Ive read about all sorts of problems from insufficient driver support to blue screen of death to some dark ritual involving window vista disks and fire....I highly suggest waiting for at least 6 months or so, vista is new and it just needs time to go through the whole patch/debug mode. I eventually want to switch to vista, AFTER its been on the market a bit and everything smoothed out, then I would say it would be a great choice. But, the question was, what os I would use if I was building today, it would be Windows xp prof.