Saw that movie yesterday.
Short (general audience): descent movie you can watch in theater.
Long (my opinion)
[spoiler warning]: if you saw 12 Monkeys (
http://www.imdb.com/title/tt0114746/), Deja Vu (
http://www.imdb.com/title/tt0453467/) and The Proposal (
http://www.imdb.com/title/tt1041829/) or The Princess and the Frog (
http://www.imdb.com/title/tt0780521/), then you can go and see something else. Source Code has the bits, pieces and ideas from all of them. From decent beginning, through few good moments in the middle to annoying "happily ever after" end.
Moreover, rules set in the movie's world are inconsistent and illogical. Star Wars' light sabres and Strange co-piloting Millennium Falcon are fine by me, 'cause they are within logical boundaries for the world Star Wars is about. But basing movie on 8-minute short term memory of one dead person, and presenting parts of world that person didn't see (inside of one of the Metra station) is just stupid.
[/spoiler warning] Or I just had enough stupid, happy ending movies... I highly recommend watching 12 Monkeys, or Man on Fire (with Denzel Washington but better than Deja Vu) again.