I thought it was a pretty good movie. There are some criticisms I could make, but in general I thought it was an interesting concept and it was handled pretty well.
I found it to be a very heavy movie--lots to think about and interesting character studies. I spent a lot of time afterwards pondering the nature of change, privilege, loneliness, and what gives life value.
While I found bits of it to be funny, comedy definitely wasn't the focus of the film. It's not supposed to be funny. One of the central theses is that funny people are often pretty screwed up.
I do think it was marketed poorly--people didn't really know what to expect, and Adam Sandler tends to attract an audience who would NOT appreciate this movie at all. It was, as a PP mentioned, sort of "inside" for the entertainment industry.