Just did a whole round of Vista vs Mac OSX debates, and there are links to them on my blog:
http://fredtime.com.
Basically, Vista is too new to risk upgrading to at this point. Drivers are still crashing... I tried using the MOTU Vista drivers with my PCI-424 card and KABOOM: the blue screen of death!!!
It will take a very long time before, as Sharp says: "Eventually everything will be Vista compatible only." Microsoft has really confused the market by offering 6 different versions of Vista, and I think they have priced it too high. It could be years before even half the XP users have upgraded, and that will keep developers from making Vista-only software... they would lose too many sales.
Despite all that, as I mentioned in the videocast that is linked to on my blog, I will say that Vista has a much better audio engine than XP. Right now there isn't any "killer audio app" that requires it... but if some company comes out with one, then maybe it would be worth upgrading.
So, stick with XP if you are a Windoze user. If you are a Mac user, you can actually install Vista on your Mac, but I wouldn;t recommend that either! All you need to do is wait for OSX Leopard
Fred