Tilda Swinton's acting in this film is phenomenal, and makes it worth seeing on that account alone.
The directing, editing and cinematography were all successful in creating a fast-moving narrative that constantly teeters on the edge of Bad Things. The magic in all this is that, unlike so many mainstream films, none of the above comes at the cost of character development.
In the first half of the film, specially, we're treated to emotionally charged scenes between Tilda and her (limited) inner circle. These interactions are portrayed in a smart, stylish manner, revealing inner complexities without delving into melodrama. Some of these scenes are hard. Unfortunately, in the second half the film tends to focus more on the gnarled plot, and what character points it makes tend to be re-iterative rather than new. Once we've grasped the essential contradiction of having to like such an unlikeable character, the second kidnapping and related scenes of suspense in Tijuana become somewhat indulgent and perfunctory. I was disappointed by the ending which, despite the film's generous running time, felt rushed, and in pointed contrast to those earlier, more possibility-laden sequences.
Swinton is fantastic, but as Roger Ebert mentions in his review, kudos should also go to Saul Rubinek, one of my favorite character actors. (Who else could deliver such memorable performances in productions as varied as Star Trek: The Next Generation, True Romance and Frasier?)
Ebert picked this as one of his "Top Ten Independent Films" of 2009 (he has a total Top 20 films in two categories).