I have a mixed set of results. I brought the upgrade and used it since the day it was released. I use Vista 32 and XP for VS2008 (vista) + SQL2008 (on XP) .NET C# Winforms development.
I was happy (despite the awful bug with Exposé + Unity where VMware won’t correctly show the content of Windows windows (lol) when in Exposé), and I think is an improvement over VMware 2.06. It’s faster and has a few more options (The menu is nice as already mentioned).
However after following Parallels on twitter and the mixed results, I decided to give Parallels 5 a try. I had a Parallels 1, 2 an 3 license, skipped 4 in favor of VMware.
Parallels 5 compiles and works noticeably faster within VS2008. The compilation clearly takes less time (didn’t benchmark but after almost two weeks working with a product, I instantly saw the speed increase). My application uses a lot of GDI+ code. I was shocked to see that it was that fast (I was always complaining about slowness in GDI+!). Parallels runs circles around VMware in that aspect.
I have a powerful box (Mac Pro 8 cores 10Gb RAM) but I had that before, so no change between both products. I have them both and I occasionally switch between them (svn update and good to go). The VMs have been converted from VMware to Parallels, so I assume that any reinstall will be even better for Parallels (waiting on Win 7 to try both on a fresh install).
Despite all this, Parallels 5 has bugs too. Some details. I’d say you give it a try. Some people think that CPU usage is all that matters, but I don’t agree. VM responsiveness and day-to-day work is what matters. So far, I prefer Parallels. Stil 13 trial days :)