It was good but I had it pretty much figured out about halfway through.
Really? cuz after watching it I still couldn't figure it out.
SPOILER
Sure it's easy to have guessed that he's crazy... but there were a lot of subtle things that lent themselves to questioning whether he really was crazy after all, and that is what left me wondering.
If you accept that he's crazy and it was staged, the question is how much of it was staged and how much was in his imagination? If all the conversations he had were real, especially with the other mental patients, then it casts some doubt.
I forgot what he says at the end, but that also granted a lot of ambiguity about the whole thing.