It does provide a bump over the cheaper GT 120, but as Rich Brown says, it only pushes the Mac Pro's gaming performance from "mediocre" to "acceptable." And this is on his $3499 review machine.
Obviously there are way cheaper and more powerful Windows alternatives for gaming, especially if you build your own, but the option for an even awesomer (if pricier) graphics card from Apple, like a Radeon HD 4870 X2, would be nice. We know the Mac Pro isn't built for gamers, but still. Let's hear your best "Macs suck for gaming" comments below anyway. Be clever, people! [Crave]