I watched this the other night when I was drunk. Because of this, I don't really have any kind of clever insights into the film.
The only thing I can say is that I'd forgotten how miserable this film makes you feel about relationships, and how awful the characters are (apart from Clive Owen and Natalie Portman, who I kind of rooted for).
Still, it nails this greedy, horrible human spirit that seems quite pervasive in the world of relationships. 8/10