Just saw this.
It has a silly premise when it comes to a person believing a 90 min diagnosis, but I enjoyed how his behavior was explained.
I've read a few reviews and the general dislike falls into these categories:
1. Milan Kunis isn't a good actress
2. This was not a pure comedy
3. Believing the 90 minute diagnosis
4. The timing of Robin Williams' suicide with a film involving this subject matter.
I didn't mind these issues. If you do, then you may want to skip this. Personally, I like the film.