“Those improvements can make your current hardware feel faster despite the fact that your CPU can’t magically crunch numbers any faster,” Foresman reports. “The changes also lay the foundation for Apple to update OS X’s OpenGL support in a more timely manner, which could potentially lead to better graphics performance in the future.”
Foresman reports, “Improved drivers appear to be working in concert with overall improvements to OS X’s graphics subsystem. According one source who spoke to Ars on the condition of anonymity, Apple has significantly altered the architecture of the graphics subsystem in Mountain Lion, cleaning up the interface between OpenGL and drivers in order to implement upcoming support for OpenGL 4.2. OS X currently supports version 3.2…”
Much more, including benchmarks, in the full article here.