I'm a bit late now, but if I would have seen your reply earlier, I would have linked you to another thread that I started where many many people of all different systems were talking about the 8800GT's performance. We all kind of settled on the fact that it's not as good as it should be. Oh well, here it is if you are at all interested:

http://forum.insanelymac.com/index.php?showtopic=89001

Feel free to skip past the parts that talk about EFI strings.