Even though I still firmly believe Apple should be using dedicated graphics and not integrated, I have to admit I'm impressed with the performance.
It's definitely a step in the right direction. It is a good performer, though still behind the GeForce 8400M GS and 9300M GS.
I wouldn't put too much hope in 3DMark scores either. 3DMark is highly inaccurate and very easily manipulated. ATI and nVidia have both been found guilty of manipulating the results via driver tweaks.
But this is a good solid performer. A huge step up from Intel. But, again, Apple needs to be using dedicated GPUs. Not integrated.
I would be curious to see, in person, how well it runs UT3, GRID, and HL2 EP2. If it can run those even at low/mid settings then it should be able to push GTA4 at low/mid settings.