One thing to keep in mind (and I do like XP Mode) is that it "fakes" the hardware environment. This works fine for most XP programs, not at all for others. My housemate is a college professor and I tried to use it to get a Powerpoint plugin to work properly (good old Adobe apparently can't be troubled to write an effective update for their http://www.adobe.com/products/presenter/
$500+ software) and it refused to do the audio recording. (Which for that program is kind of the point...)
It never hurts to try, though. For many programs it can save you from the hassles of a dual-boot system.