In my point of view, expectation is an important element regarding the experience of watching a movie. In the case of "It's kind of a funny story", the audience, after watching the trailer may have the sense that this is a superficial movie. That is not really the case.
The movie tells the story of Craig, a teenager on the verge of deciding his career (college application) and after having suicidal thoughts he checks himself in a hospital's psychiatric floor. Once there, he bonds with some of the other patients. Eventually, Craig feels better about himself after take a look at life through the eyes of his new mates.
The central theme of the film is very deep as something like "how do you want to live your life versus how the society compels you to live it". Some of the characters presented in the movie simply didn't know how to react in the society at some point. They have that in common.
There's when the film gets really meaningful. If you think about it, they really get better inside the facilities of the hospital because a new artificial society (composed by the patients) is created. It is a very simple one. Manageable.
The movie also have some comic relief and well dose out. Zach Galifianakis is something else in this movie. The only other movie I've seen featuring him was "the hangover". When I found out that he would play a mentally disturbed character, I thought "again??". Here, is a little different: Galifianakis' character shows bits of drama, comedy and, yeah, dumb crazyness. All well performed.
I've never heard of Keir Gilchrist but he seems a nice actor and he is very good in the "flashback" scenes.
Two last thoughts: the Queen musical scene is cool and Emma Roberts is very pretty.
So, "It's kind of a funny story" is a very fluid movie to watch and has a meaningful message. The acting is very good and probably will please different kind of audiences. The movie deserves an 8. Check it out.