thank you for this - I was able to bump GTA IV to Very High and I got solid 39FPS!.. and thats very high on everything (water, shador) and I also just bumped up Dragon Age 2 and got very smooth gameplay.
what resolution - settings ? can you post a screen shot ?
i've 2.3GHz 8GB RAM, 2011 MBP. also latest ATI drivers and OC to 800/950
benchmark in GTA 4 gets average 31fps 1920x1200 on default high/medium settings, but when i actually play, it's not smooth at all. choppy, stuttering etc.
even with lower resolution 1680 * 1050 and all medium settings it doesn't seem to make a difference.
ps: it actually almost feels slower than with 2010 MBP with 330M.
did you do any tweaks - any stuttering ?