It wasn't perfect, certainly. The extended musical cues were pretty bad, especially the overused Under Pressure. Goldthwait clearly doesn't have an ear for incorporating music into his films. Also, once Robin Williams' character started to exploit the situation the movie lost a little something. It had a nice balance of dark humor and emotional honesty going on, and the movie suffered a bit when it started to push the concept of passing off his writing as his son's, the notoriety it brought him, the portrayal of how the students made the son into a hero, etc... Although the film was never supposed to be 100% realistic, it was a satire, it lost some of that honesty.
But at its core I felt the movie was really original compared to most of the comedies put out nowadays. It had a lot to say about how we deal with grief, how we exploit tragedy, how we transpose our pain onto other people, and how generally insufferable teenagers are.

It is a deeply cynical work.
But donkey balls? Really? Interesting point of view.