Parrallels vs Fusion Round II
vmware2
After spending some time running both virtualisation products side by side, here is my list of Pros and Cons:

Parallels:
Pros: Disk Snapshot manager in Parallels in V3.0 is awesome. Having the ability to choose between multiple snapshots is incredibly useful.

Cons: No matter what I do, Parallels impacts on the rest of my system. Resuming from sleep still sees me waiting for random spinning beach balls that only occur when parallels is running. Also Parallels is messing with my expose at the moment... for some reason, it stops working on the hot corners I have assigned, but ALT-Tabbing to the Parallels VM brings it back.

VMWare:
Pros: Fast. It is noticeably faster than Parallels. It just FEELS sleeker.
Expose works on individual windows rather than shunting your invisible desktop around.

Cons: Unity mode is hard to manage when you want to select the VM and return it to windows in a "window".

So far, VMware Fusion has won me over enough to convince me to run it as my work virtual for Exchange / 'windowsy' things for a while to see how it lasts...