On the one hand, Green Zone is a preposterous and Hollywood-simple rendering of the faulty reasoning for Iraq War II. On the other hand it's a smartly-critical action film which weaves politics with morality, the result of which is that I often found myself guilty because I didn't know who I should really be rooting for. The screenplay was written by Brian Helgeland (L.A. Confidential), and his hand is delightfully easy to spot.
The visual scope of this film is quite impressive, with much of the landscape of post-invasion Baghdad effectively similar to the one delivered to civilians by war reporters. References to war time events are accurate enough to make everything as plausible as it could be. Unfortunately, a scene in which Matt Damon outruns and outmanuevers the special forces (branch?) commander undercuts much of the meticulous work of the rest of the movie.
Details to watch for; the outgoing AA tracers reflected in the car windows during the "shock and awe" attack, the ad-hoc "US" taped to Freddie's roof to identify him as friendly, the visual confusion of who the contractors are and who the soldiers are.
At times, Matt Damon's performance wavers from the blank idealism of a midwestern solider (Pvt. Ryan?) to that of a moral leader; so much so that it is hard to tell what Miller's real motives are. In fact, most of the cast are so busy moving the plot along that there is little sense of actual depth to the people themselves. It's all decision and action, which is fine, but don't expect great performances.