I agree with the 4 stars.
Disregarding the creative license they took with the story (in reality the CIA was a junior partner to the Canadians in getting the hostages out, they did not stay at the embassy but employees of the Canadian embassy risked their lives harbouring them, etc.), I thought the movie was very well done and maintained tension even though I knew how the story was going to end.
The only gripe I have is that I wish Ben Affleck would stop casting himself. While he wasn't bad in this one, I prefer him as a director, not an actor.