There are very rough patches in the game and the Capra Demon stage and Blighttown (with which I personally never had a problem even at ~ 10-15fps on PS3) are probably 2 of the stand out regions (along woth Tomb of Giants .. god, did I hate my first time through that), but that's also why for many it's probably the most charming title in the Souls series (for me that's Demon's Souls) - there are clearly many experimental things in the game and the later titles just feel a bit too streamlined.