I was one of the people who had no problems with the game 40 hours in but as soon as my save game reached the 5,5 MB threshold, the game became very clunky.
I also noticed that when I pressed the PS button to quit the game, the screen didn't respond immediately. This leads me to believe that the save file is just one of the problems.
There seems to be a bigger performance issue with this game on the PS3 and it has nothing to do with overheating or aging SKUs.
I have a feeling that this will prove to be a huge fiasko in the end!
