Depends what you are doing. Because of some driver issues, it can be slower for some applications.
In terms of the OS itself, it is a lot faster than XP.
I have been using Vista since I built a new box, and have really enjoyed it. I have had a few random re-boots that signal not quite all the way where it needs to be, but in terms of speed and performance, booting up getting into the os etc it kills XP.
I also have a 4gig flash drive I use with Readyboost which can help performance a bit too. People mistakenly think Vista uses more resources than XP. The reality is with their better caching Vista uses your memory better. It not only keeps track of which programs you use, but when you use them. So if you run some program every day first thing in the morning, it knows this and will have it cached in memory when you go to bring it up it will come up very quickly.
Leaving DRM issues aside, I have been pretty happy with Vista so far, and I am not one to normally jump on the OS bandwagon early.
I have 2 gigs of ram and use the readyboost feature, but for anyone under that, I definately recommend it. It basically acts as a smart cache where it can access small bits of data much faster than retrieving them from the hard drive. I have seen tests where people with 512 megs of ram saw up to 25% performance increase with readyboost.
My last vista driver just became available yesterday too, so everything is working pretty well now.
