I have been running Windows 7 on Parallels 5 (build 188.8.131.524) on Mac OS X 10.4.11. I used the "hack" to get Aero to work (the video.dx_profile=6 switch). Performance of Aero was very good on this system. Yesterday, I upgraded to Mac OS X 10.6.2. I removed the video.dx_profile=6 hack, as aero is supported on Mac OS X 10.6.2 in Parallels. The first thing that I noticed was that Aero graphics performance slowed waaaaaaay down. I had to disable window transparency to get the system to a tolerable state. Is there something that I'm missing? Shouldn't upgrading to Snow Leopard have increased the performance?