This movie came out of nowhere and surprised the heck out of me. It's stunningly original, and captivating from start to finish. The humor, while supremely stupid, is great and well delivered, and the mystery of what happened the previous night is solved bit by bit in a very satisfying manner. The acting is great, the end delivers, and the pacing and general cinematography are top-notch.
One small problem I had was that I slightly disagreed with the message, as it was backed up by huge sophisms, which might lead one to assume a position that isn't... nuanced enough. Still, if you just look at the big picture, the moral is true.
In a sentence:
Very original, very well made, very funny, and VERY stupid. Dare I say, a future classic.