- Out-Of-Box Support for GTX 500 Series
Mac OS X has supported NVIDIA's GTX 500 series of graphics cards for a while now, thanks to the release of official Mac OS X drivers by NVIDIA itself. However, in Mountain Lion, the need for drivers is removed altogether-- everything works natively.
- Out-Of-Box (?) Support For Radeon HD 6900 Series
This one is long overdue. In OS X Mountain Lion, graphics cards in the AMD Radeon HD 6900 series work out of the box on real Macs. The results on Hackintoshes themselves are still mixed, but full support should be coming soon. There has been preliminary graphics support for the 6900 series ever since the initial release of Mac OS X Lion, but actually getting the cards to work has been a whole other matter.
- No Support For 32-Bit Kernel
OS X Mountain Lion cannot boot with the 32-bit kernel, meaning that Hackintoshes will no longer be able to use the "arch=i386" boot flag at startup. This won't affect most users, since every version of Mac OS X has booted from the 64-bit kernel by default since the release of Mac OS X Snow Leopard. However, if you have to boot your Hackintosh with the 32-bit kernel for one reason or another, this change in Mountain Lion may cause you problems in the future.