playing it with my 2011 imac 27" with 1gb 6970m. mostly its okay, in fact i can play it in 1080p in low settings around 40 fps. but when i get into a big fight scene it drops to slide show levels, sort of 15 fpbs. for these i need to quit, reopen and put on the lowest graphical level and then its playable, 30 fps or so. anyone else punishing themselves by doing this? any thoughts?