Apple upgraded the graphics system in ML significantly. And most of what I'm reading is that does make it faster than Lion for later Macs that support off-loading processor cycles to the GPU. With my 2008 Mac Pro, that's what I'm finding. It seems a lot snappier with ML than Lion. It also has 16 gigs of RAM and the mid-range graphics card.
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Eric

A pizza with radius "z" and height "a" has a volume calculated by pi*z*z*a.