I use my computer primarily for Aperture but also do some gaming and want a QUIETER and faster card.
Somewhere else someone posted that this card is pretty noisy. Looking at it being a single-slot solution (which is not required in a MacPro btw. as Apple thankfully designed the first PCI Express slot double-wide, so you can put a double-slot card in there without restraining other slots) this might well be the case.
As i was looking for a nearly-silent card as well i opted for the limited edition of the MSI 7900 GTO. That card offers nearly the performance of the former flagship 7900GTX (for a - back then - much lower price) while keeping the whisper-silent cooling system of the 7900 GTX. It's only available used these days and you better watch out as many owners tried to overclock it...
All that was needed was a modified kext and a simple change of the card BIOS (google for NVinject, or NATIT / TITAN, with NVinject doing the necessary actions automagically). I'm using this card together with the factory standard 7300GT plugged in slot 4. Each one drives one monitor (had no luck connecting a third monitor though - was being recognized as 640x480 only without showing a picture or not recognized at all).
With the 7900GTO i can play WoW (has been asked here for) at 1920x1200, all settings maxed out, around 30-40 fps in the "new" world and around 60+ fps in the "old" world. I do notice a short slowdown sometimes, caused by the comparably slow harddrive access when changing locations by porting (a harddisc raid setup might help there).
Under Tiger (10.4.11, switch to Leopard procrastinated) daily work is smooth, QuartzExtreme with all the Core effects works flawlessly and even though i have to drive my old 23" with an analog VGA signal to make full use of the 1920x1200 screen (DVI only allows for up to 1600x1200 on that old monitor) the picture quality is still very impressive (i noticed that many cheap graphic cards today offer a sub-par image quality above 1024x768 when using analog).
One "drawback" is that the card gets initialized properly only after the system has started to boot. That's one reason why i kept the 7300 in there, as one would otherwise have no startup screen in case it's needed (the Login-Screen is visible on the 7900, no problem there).
Ah yes - another annoyance is to get the proper power supply cable for that video card, as Apple opted for an unusual micro-connector on the motherboard end (means a "standard" cable does not fit), so you have to find a dealer that orders you that special cable as a spare part from Apple (normally it is not available for a normal purchase), which causes you to pay a premium!
I don't regret it however, as the card has lots of horsepower and is absolutely not audible (in opposite to e.g. that infamous X1900...). And back then there was no real choice amongst silent cards in the MacPro.
