What do you make of the ending of American Psycho? Personaly after reading the book and the film I think he did commit the murders but everyone was too swept up in their own shallow lives to notice.

I was wondering about that myself, but i haven't read the book, so i only have a limited perspective on it. I actually think that he didn't do it, and that was all a part of his insanity. he wanted to do it so much, that he thought he had.
I decided that when he walked into what he thought was Paul Owen's appartment, where he thought he'd left the gory remains of multiple victims, and the woman living there seemed quite established there, even though it had been re-painted which seemed to hint at the murders.

Although, it might be more a choice which the reader/watcher has to make, a question left unanswered. Maybe Bret Easton-Ellis didn't mean for there to be a reality to the murders, maybe it was just meant to be undecided, so that all paths could be explored