Very good movie overall, highly recommended. Most of the negative reviews don't have any merit and are all pollitically based. Give this movie a chance at least, and it might give you a different perspective.
The thing I enjoyed most about the film is the fact that it doesn't shy away from being a super-sized-cliche;
While it doesn't offer any answers, it both thrills and makes you think.
The film's masterful storytelling did its job. The message was clear. No need to overdo.