When I first considered getting Fusion, I looked into Parallels. We had Parallels at work, and I wasn't impressed. It ran slow and the support from the company was pretty much nil. So, I went with Fusion.
I've been using Fusion for a while. I don't have Fusion3, and prior to a few updates back, it ran virtualized Windows and apps great. Now, it's much slower than before. One thing I like about it is that although I have Windows setup in Bootcamp, I can also reach it while in Snow Leopard through Fusion, thereby allowing me to drag files and run them in both systems at the same time.
However, I agree, that booting into Bootcamp is best for this kind of thing.