Ars Technica posted a review on Parallels Desktop 6 for the Mac

It has been less than ten months since we reviewed Parallels Desktop 5, a competent but buggy release from Parallels. Shipping paid updates with stability issues seems to be the company's modus operandi, so I was a little skeptical when I saw that a new version was already being released, since the last one had so many issues that needed ironing out. The feature list of Parallels Desktop 6 isn't what I'd call ambitious—the main focus of version 6 has been on the 64-bit host and increased speed, mostly for 3D and gaming. Gaming was already Parallels' forte, but I was curious to see if the new version would finally make playing modern games with complex shaders, high resolutions, and high-quality audio a reality. If it doesn't come through, and suffers from stability issues, this could be a disastrous release for Parallels. Read on for the verdict.

  Parallels Desktop 6: The Ars Review