The movie is powerful as a political statement about extraordinary rendition, torture and the politics of the war on terror. Others have already commented on these and other aspects of the movie. My review may contain spoilers, so if you haven't seen the movie, you may not want to read beyond this point.
Several questions are raised by this movie. First of all, was the protagonist guilty or not? There is no satisfying explanation for why the NSA decided to have him picked up and rendered in the first place. Is there an innocent explanation for why he got phone calls from what the NSA thinks is a terrorist? If there is, the movie does not seem to give one and that made the whole movie quite unsatisfying to me. It is all well and good to make statements about whether torture is right or wrong, but first prove to me that they tortured the wrong person, then we will take it to the next step.
If the protagonist was guilty, then what was achieved by releasing him? Perhaps, we was well-trained to resist up to a certain point and then pretend to break down and give answers that can be proved wrong with a little research, thus tending to lead the torturers to believe that they had tortured an innocent man into confessing without actually being guilty. However, there is nothing in the movie that proves he is guilty either.
The various other loose ends out there are: 1. So, a rogue CIA agent has him released and flown back home. What prevents the NSA from picking him up again? A little publicity in the Washington Post? Please give me a break here... If a senator is not willing to put his neck on the line to intervene on his behalf, what does Corinne Whitman have to fear? 2. If the NSA has been tracking what phone numbers are being called by whom, why couldn't they listen in on some of the calls to figure out whether anything underhanded is being discussed? 3. The plot is even more stupid anyways. Any criminal with more than a dozen brain cells would transact his criminal business on an anonymous prepaid cell phone line, not on one that can be traced back to him and his house.
The whole movie revolves around tugging at the viewers' heart strings by showing graphic and gratuitous scenes of torture. But when you think about it with any more depth, there is nothing of substance in this movie, only plenty of unanswered questions and the feeling of "what, that is it?!!!" at the end of the movie.