Actually, I was (and still do) use VMWare's
Fusion, which I find to be stable and overall does a good job.
I had first used
Parallels, but found it was buggy and on a few occassions I completely lost my XP data and had to reinstall the system. A real pain in the neck! When I contacted their support for help (located in Russia), it was frequently more than a day to get a response, and the responses were canned and not helpful. (That was V3 I was using from Parallels - they are now on V4, but I don't know if their issues are solved.)
The benefit of VMWare (and Parallels) is that one can have both the Mac OS and the Windows OS (XP or Vista) running at the same time, and one can jump around (e.g., listen to iTunes while working on your XP machine). VMWare's website is a nightmare of technical jargon and confusion, Parallels website is more user friendly.
Bootcamp basically partitions off your Mac drive in a way that you can run the Mac as a Windows machine or a Mac machine, but not both at the same time.
My vote (for now) is VMWare Fusion.
