I've finished it once, no kills (bar bosses), saved in the final room so I could see all four endings without doing four playthroughs. Started another playthrough on the hardest difficulty. Am nearly at the Barret fight, but haven't played it in a while. I thoroughly enjoyed it, but the boss fights were kind of annoying (although it is the first game I have encountered where I only had trouble with the first boss, and all subsequent ones were really really easy by comparison).