I too am not doing too hot here on a MacbookPro 15" Mid 2011 with HD ATI 6750M.
Getting only 35-38 Mhash/sec or so
I'm running the Bitcoin app with gui, and have DiabloMiner running in terminal (I assume bitcoin.app runs bitcoind under the hood of the gui).
Will attempt: installing the pyopencl items and will attempt to use the other miner and report back. I'm forcing the discrete chip to be used with gfxCardStatus menu item. I have some work open in various apps currently- will attempt to restart and retry tomorrow as well.
Any tips greatly appreciated.