I wanted to see this movie as soon as it came out, but I just didn't get around to it. I was impressed for several reasons, the main being an innovative technology that drove the plot. Gyllenhall's character is a military captain, and a new program, called the "source code," basically uses the declared dead soldier's half-alive brain in order to send him back in time and act as a spy inside another person's body. Sounds confusing, but screenwriter Ben Ripley explains it all thoroughly and clearly early in the movie. In addition, the repetition of the same eight mintues with different results each time make for an interesting "what if" experiment a la Sliding Doors.
The acting of both Gyllenhall and Monoghan is spot-on, bringing emotion and depth to a movie that could have been too stiff and scientific due to the out-there technology and concept. The emotion they bring echoes one of the most important questions of the movie: If you knew you only had eight minutes to live, what would you do with that time? While this kind of thinking could run you ragged, it does encourage the concept of living in the moment, going for what you want, and not letting life or opportunities pass you by.
The subtle changes that Ripley writes for each of the travels back in time that Gyllenhall's character experiences are also a study in human behavior. Our little communication quirks, our laziness, and how we tend to disengage and float through life. This movie shakes the characters awake and gives them a second chance.
A clever plot combined with crazy-smart technology and solid acting equals a movie worth watching.