OS X 10.8 vs. Ubuntu Linux: A Battle With No Clear Winner
When it comes to the Sandy Bridge graphics, OS X 10.7.4 and OS X 10.8.0 were both much faster than the current Ubuntu Linux graphics state for the open-source Nexuiz game.
The ioquake3-based Urban Terror game was also much faster with Apple's graphics drivers for the Intel HD Graphics than under Ubuntu Linux with Mesa.