For what it is and how it works Quartz is a remarkable piece of programming. Currently however, their are no sufficient drivers or hardware to adequately allow the GPU to tak over the GUI control any more effectively than the CPU does now.
The poblem in this case is that in being forward thinking Apple out[aced hardware. new drivers are expected and there's a lot more performance to be wrung out of the graphics layer itself, but, the serious speed bumps will come with new Graphics cards, or perhaps, as has been limitedly speculated, a daughter card to handle the 2D rendering.
There are extensive discussion about Quartz optimization all over these fora andover at MacNN. Do a search, you'll get more information than you care to know!
Ciao!