I thought it was excellent, less of a science fiction story and more of a psychodrame where failure resulted in suicide. The cinematography captured the changing moods perfectly and Sandra Bullock delivered a perfectly calibrated performance. The weaknesses lay in the lack of credibility of the film's premise. How, for instance was the electricity still working in a post-apocalyptic world? How come the criminally insane were unaffected by the alien presence. But these are minor quibbles in an engrossing tale with a brilliant and unexpected happy ending. And we all love happy endings.