Haven't read all the posts in this thread, but I just upgraded my Hac today with a EVGA GTX 550 Ti and it worked out of the box. I had Intel integrated 3000 video before, which gave me artifacts. Those are gone. The only issue I had was a panic upon reboot. I decided to rerun MB v4.3 and specified the 10.7.2 Nvidia option (along with my other selections) ... I rebooted without incident. I guess time will tell if this is truly safe, but if everything is stable, then it was as simple as 1) install card, 2) tweak bios to look at new slot if not on auto, 3) boot up, 4) run MB, and 5) reboot.
I picked this card because it was supposed to be OOB compatible. It wasn't coincidence that I have the card I have. After messing with wifi, I place a lot of stock in picking extremely compatible components for my Hac!
I have this card, I didn't build my system specifically for a hackintosh, but rather turned my windows box into one when I got fed up with blue screens of death after every power outage. Anyway. I have it working sort of. the OS acknowledges that its whats plugged in. By that I mean that in the system profiler it says gtx 550ti. But it tells me 1.5gigs instead of 1,the screen seems to have the overscan underscan issue where it either rolls over the display space of the screen or gives a 1.5 to 2 inch black boarder, and I'm still not able to use Opencl. I don't know if cuda is installed correctly as for some reason i don't have frontrow installed. It just didn't install with the system...could be the install disk I used. Anyway if anyone has any suggestions as to how to fix these problems I'd be very much interested. So far I've installed the main cuda drivers from nvidia, installed the kext's as part of the multibeast install (the combo update) and I've installed the nvidia drivers recommended in one of the threads. All with no luck
Did you try adding an efi string to your org.chameleon.Boot.plist? That was the only way I could get mine to work. I have everything working, but something isn't right. Youtube videos lag sometimes and my dock is a little jittery and now quite as smooth as it should be. I dunno, I am just living with it right now. I am considering a different graphics card though.
I got it to give me ripples inside dashboard, which turned out to be an ID.10.t error...but anyway all i had to do was turn off the little thing that made it part of launch pad. That did it...anyway now I'm having an issue with quicktime and frontrow giving me blue swirls and such in full screen mode.