In multiplayer with 3-4 people and a large mob of enemies... the framerate is going to drop.
It's not gamebreaking I guess but it's a pretty significant drop that can be very frustrating. If you're just into singleplayer there are some slight framerate drops but nothing too major imo.
edit: would recommend looking into Silent Hill: Book of Memories. Similar dungeon crawler gameplay but supposedly the game is much better. DH:A isn't very highly regarded. I enjoyed it quite a bit but it's still quite flawed.
Haven't played SH:BoM myself though. I have it on my shelf but I just haven't got around to it.
edit2: let me know if you see this! would like to know if I was in time or not :p