When I first saw the traielr for this, I feared it was going to be some big rip off of One Flew Over the Cuckoo's Nest, and, while there are traces of that, the film thankfully is not that, and is its own little thing. That, and since Fleck and Boden were behind it, I got the feeling that this seemed like the sort of film they'd make anyway.
While the film is a little underwhelming and feels a bit too precious or indie, or trite and a little too neat and tidy (which is actually addressed in the film), I liked it. I wanted more, but this didn't leave me unsatisfied, either. The writing was a little weak, and Craig didn't really seem like he needed to be at the hospital, but I found myself able to relate to him and some of the other characters...maybe more than I'm comfortable with, actually.
Where this film really shines is with the acting. As others have said, Galifianakis knocks it out of the park, showing that he really does have some legit and serious acting chops. He gives a really nuanced performance that seems like we knew he had it in him, but just needed to see it to be sure. I look forward to seeing him do more stuff like this. The rest of the cast is good too. Lots of known names and faces, but not in a gimmicky stunt casting sort of way. Galifianakis owns this one, but Emma Roberts is also really quite good, and also achieves the right balance given the type of character she's playing. Keir Gilchrist is not bad as Craig, but I think could have been just slightly better.
While this film didn't grab me like I thought it would, it's decent enough, and should be pleasing in some way for just about anyone who sees it.