Two things first it sounds like your machine, and not the game, so make sure to put it in a well vented area, and to thoroughly clean it. Also make sure to not play your game for more then few hours at a time to avoid heating problems. Another thing, and this is important TURN OFF YOUR AUTO SAVE. I have heard that it causes massive in game stuttering, and frame rate issues as the constant saving every time you enter in to a new area hangs up.
Oh, I haven't tried it yet, buying the game tomorrow. I'm just worried about it happening, that's all. Also, it's not the auto-save stuttering, that I can live with. It's clearly something else, unless it autosaves every 2-3 second, and it doesn't explain the 1 minute-loading when entering/exiting citys and buildings.
Anyways, I'll clean my ps3 free of dust inside, put an extra fan pointed at the ps3 AND deleting lots of stuff from it to free space. Hope it works.. =/
Edit: Haven't heard about any ps3slim users having problems, so that sounds about right. Just the elder models.