Overall I liked it. The ending was a bit odd and ambiguous, but I think that was the director's intent.
One thing I did not like was at the beginning. Nicholas Cage's character was asking his class about determinism. He states that if the universe is deterministic then that means everything happens for a reason. That is completely false. Determinism has nothing to do with purpose.
He also babbled on and on about how improbable it is for everything to line itself up "perfectly" for life to be able to evolve on our Earth. Sounded a bit like creationist propaganda to me, but maybe I was reading too much into it.