This is pretty much Jack Black for 85 minutes. He was kind of shoehorned into the classic story because some Hollywood executive (or Black’s agent, or perhaps Black himself) thought that the concept could be a good showcase for Black’s unique brand of humor.
So, if you are big Jack Black fan, then you’ll probably love this movie. If you hate Jack Black, then you’ll probably hate this movie. If you don’t have an opinion either way, this film film would probably sway you to one side or the other. Therefore, your mileage may vary.
Regardless, Emily Blunt passed on doing Iron Man 2 to do this film. It would be interesting to see how big of a mistake that was.