I work with computers and have all kinds of machines, including Mac and Linux. I have to keep up with different OS's.
I have Vista on my work desktop at home. The part I like about it is that I find the new interface faster to work with. It's ergonomically more fluid than XP.
The worst part of Vista is any network file operations, or copy/paste to external drives. It is an absolute disaster. If you do work over the network to XP machines don't use Vista.
I also test a lot of software and Vista is a crap shoot when you install programs. I have an image backup I use to restore the OS drive and I use it at least once or twice a month when something ganks the OS.
On the other hand, I have it on my wife's machine, who just uses it for her school, web and office work and it's been great. She likes it. It handles web media very well.
Customers I have who aren't power users are OK with it as well.
Bottom line, if you work with network files a lot, or like to tinker with new software, stick to XP, otherwise you may like Vista for the way it organizes how you work.
Thanks.