Cuaron's masterpiece so far (including Gravity, which was gravely miscast). This film is: a) easily the best film of the decade of the 2000's; b) the finest dystopia film since 'A Clockwork Orange' and probably the best sci-fi since '2001: A Space Odyssey'; and c) all the evidence you need that Clive Owen should have been selected as James Bond in place of Daniel Craig. Heartily recommended to anyone interested in how great both science fiction and cinema can possibly be. You may be depressed with the state of both the world and mankind, after watching it, but you won't be disappointed in the possibilities of cinema.
A strong premise and great cast prompted my interest, but the movie falls short of its promise. Clive Owens gives a great performance and a few of the scenes are remarkably memorable and resonant. However, there are very long stretches where the movie simply stagnates and the plot drifts away, especially towards the end. Overall, it's rather melancholy and despite the "action" scenes, not especially thrilling. If you like sci-fi movies set in dystopian futures, or are a big Clive Owen fan, you may still find it worth watching despite its flaws.
An aside: One of the "extras" on the DVD has some heavily accented academic trilling at length about the movie's philosophical meaning. It's entertainingly over-the-top and almost unintelligible: jargon piled into a Dagwood sandwich of contradictory abstractions. Anyway, if you don't watch too much of it, its good for a laugh.