My PNY 7800GTX works in windows on my macpro! I had to rig a power cable through the CD compartment bay to power the card to get it running at full speed but it was well worth it. Beyond the slightly longer load times from the SATA issues, it SCREAMS! More than double the preformance of my Athlon 3800 X2 with the same GFX card and drivers. Even better, I can keep both cards in and use both in windows *(sli not supported) but both cards work in windows. It is a little hotter in the MAC but still well within its limits. When I switch to OSX the 7300 is the only useable card. The 7800 is reported in the OS but its not usable. As for the preformance, It is more than Double the PC system with athlon X2. I used doom 3's default timedemo to gauge the systems: 640x480 with all video options disabled. My PC topped out at around 105 FPS - (Athlon X2 3800, 2 GIG ram, pny 7800GTX) The mac pro Topped out at 215 FPS - ( Retail config + PNY 7800GTX) This May turn out to be a very solid PC replacement once the SATA issues are fixed. Luckily they really dont seem to be affecting real world gaming on this system. Feel free to post your questions, experiences and comments related to MAC pro windows gaming in this thread.