Unfortunately I'm getting worse result on macbook pro early 2011 where is intel hd 3000 inside. Test was made on NovaBench which is showing that graphic performance is slower. On lion i was getting about 57 fps and on mountain lion only 30 fps. Take a look.
I'm getting 642 fps on my Early 2011 under 10.8; it automatically switches to the Radeon. Do you have something forcing the HD 3000?
Probably has the 13-inch.