I also realized that many many people must be making this comparison, and sure enough it's in Wikipedia: http://en.wikipedia.org/wiki/Comparison_of_VMware_Fusion_and_Parallels_Desktop
Parallels 3.0:
- support for cross-OS file associations (SmartSelect)
- better utilities such as a snapshot manager
VMWare Fusion 1.1:
- Con: no support cross-OS associations
- bigger community, better support for multiple OSes
- 64-bit and SMP support
See also MacNotes and LaptopNotes
