First review from me:
Michael Shannon is convincing: a great portrait of a haunted man. The movie is also very touching in the way how it depicts love within a little family. Actually I thought it was a really magnificent movie ... until the last 2-3 minutes - probably unlike most of the rest of reviewers here - when the whole story collapsed into an absolutly shitty apocalyptic doomsday whatever-trash. This movie just bailed out, took the short road home to mommy for a diaper change.
Shannon's achievment throughout the movie still makes this an enjoyable film.