This is about 2/3 of a really good, sci-fi puzzler/thriller, it's an interesting combination of Quantum Leap and Groundhog Day. It's lean, it throws you right into the plot with a minimal amount of handholding. And the leads, Jake Gyllenhaal, Vera Farmiga, Michelle Monaghan, and Jeffrey Wright are all really good. The problem is, it just doesn't stick the landing, and it also depends on whether or not the audience buys part of the explanation of what's going on. (I mean the entire explanation is sort of ludicrous, but knowing it is a sci-fi thriller with a minimal of actual, real world science, no matter how much Jeffrey Wright throws around terms like "parabolic physics", you tend to just sort of roll with things.) I think it will really depend on your mood whether or not, ultimately, you like where the movie eventually leads you. Me? At the time, I thought it was sort of nice. On reflection, I wish they could have ended it as well as it began, but that seems to be an issue with a lot of thrillers, science fiction or not, these days.
Oh, one more thing, it might have been derivative, but I thought Chris Bacon, who did the music, did a really good job.