I wanted to give it 3 stars, but then I feel the message it conveys probably doesn't deserve it.
I actually find it cute in some ways; if you need a no-brainer to pass the time on a weekend, maybe. But there are problems in this movie.
First, sorry, as a psychologist, I just have to say it: all the "psychology" thrown in there is total BS. I hate it so much that never, never have I ever seen a movie or TV show portray the correct psychology. You don't have to be "all correct," even just 70-80% I'll be thrilled. But no, except for some terms, nothing is right in the film.
Second, the change of Gary from the start to the end is unrealistic.
Also, I know the movie wants us to see Madison as a "victim," someone who we should root for, but throughout the whole movie I just can't find a solid piece of evidence that she's that way. In fact, smell something suspicious. I feel it's the problem of the plot; it should give us more reason for us to sympathize with her.
Finally, the ending... well, not totally sure it's morally justified. It could be, but again the plot doesn't convince me enough.
The ratings of this movie are high, and I'm not surprised; for pure value of entertainment it's ok. Plus these are good actors who do a good job. I never trust the ratings anyway, especially Rotten Tomatoes. Those "critics," sometimes I doubt they have eyes. On the other hand, a guy in Forbes disliked this movie, but I didn't care that much for the reasons he gave.