Apparently this is a remake of the Danish movie Brødre, and it feels like a boiled down version of that story. It is definitely not a feel good movie, and if you are even slightly emotional, I would recommend watching it with caution.
I have never been a fan of Tobey Maguire, and he seems to pull the same face in almost every movie. He does that a lot here, and I was not convinced by his performance. Jake Gyllenhaal, on the other hand, does a solid job as the screw up brother trying to do better. Natalie Portman also delivers a decent performance, and the movie even points out twice how gorgeous she is, which I can somewhat agree with.
This is not an action movie but very much a drama. If you have any personal ties to the war on terrorism in Afghanistan, you might find parts of it especially moving. I have read that the original Danish version is better, but honestly, I do not think I have the heart to watch this story again.