Since Scoble praised VMware, I decide to take another look at the latest version. I own both VMware and Parallels, but I currently use Parallels.
The new VMware converter made it easy to move my Parallels VM to VMware, so I was able to run my most recent Windows VM with it. Although there’s very little speed difference, I find that Parallels generally feels smoother and better integrated with OS X. Shared folders seem to work better in Parallels, and I like that it will boot directly into Coherence. With VMware I have to manually switch to Unity after Windows fully boots and I’ve already logged in.