The story was quite alright in itself, the execution was professional but I felt strangely unsatisfied with the whole film. I think that except Gyllenhal's character the players (esp on the train) felt very cardboard like. Since he has only 8 minutes to connect to those people it would have been more satisfying to give them more extreme, eccentric and visual features. Some of the train passengers were quite ok, but most of them just fell flat.
It might have been more interesting if Michelle Monaghan would have given a much more aggressive character - the love story came out of thin air, so she had to already be in love with the guy. It would have been much more fun if she was just about to break up with Gyllenhal's alter ego. There's not enough tension and as this is a science geektion story, so nobody gives a toss about romantic love, but everybody is interested in ugly relationship struggles (because of too much WOW and Pratchett, maybe?)
And I still don't know why this scientific crap talk is still put in movies. "Parabolic analysis" actually exists as some kind of hocuspocus stock market analysis, but maybe i'm missing the pun and the great professor B. Oomerang insists that whatever happens in the movie could has happened tomorrow over and over in the real yesterday.