Since the release of Parallels 5 I have been a huge fan. Previous to that, I really liked VMware Fusion as the product was much more mature and seemed more stable. I really had no means to measure performance other than to gauge it by my perception over regular use.
Earlier this week, VMware announced their VMware Fusion 3.1 beta, which I had to run out and try. I like to keep tabs on both of these products and am always curious when either of them releases an update.
That being said, I downloaded the beta ad built up a new Windows 7 virtual machine, installed the machine additions and played around a little bit.