Well here's the deal. The new sandy bridge processors feature the graphics processor built onto the actual CPU. This is supposed to significantly speed up bandwidth. You also have to consider that the FSB is being upped to 1333 from 1033. This computer is going to be significantly faster in both gaming and general tasks than the 2010 Macbook Pro 13". You can count on it.
I went over the bench marks of multiple sites and they all indicated a 3-6 fps drop with the GPU change.