I have an identical machine, and from my brief testing this morning High settings (ie. the default) are fine as long as you set shaders to Medium (or even low if you find Medium unsatisfactory).
I have the new i7 2.66 MBP 17" with 8GB ram , Nvidia 330M and the 512GB SSD and it plays the game on high just fine under Windows 7 bootcamp. The machine you have is very similar to mine- should easily play SC2 under high settings. Better graphics drivers are still needed in OSX, however. The limiting factor for your graphics isn't your machine, its your software.
Hmm, I will give it a go tonight. Do you guy's have the same resolution as the 15" hi-res display? I am using that and running at the default resolution setting. I have also applied the changes that capped the FPS as was advised to do when the game came out. Should I remove these and put the game back to it's default FPS settings?