Man, I feel a bit bad that this type of comedy is entirely incompatible with my own tastes, because I can understand why I'm supposed to laugh, but can't. The jokes ALL fell flat for me, and I didn't even smile, despite the movie trying desperately to get something out of its audience. I think it's the SNL-style "stupid" brand of humor that just ends up feeling incredibly corny to me. The acting is terrible (except maybe Will Ferrel, who is... Will Ferrel), and in trying to be silly, the story becomes simple and a bit dull.
On the other hand, the costume work is eye-catching (obviously) and the cinematography is flashy and original (two things which drew me to watching the movie).
In a sentence:
Dull, unfunny, and poorly acted. Very original, though, and I could definitely see some people liking this (and I don't mean that in a derogatory way).