Here is my review.
Very entertaining, but is a mess. A very funny mess. This flick probably won't stand up to repeat viewings, so see it with friends your first time around.
Jack Black does indeed prove he is capable of being funny in a slapstick-type role without being overly obnoxious.
Robert Downey Jr. is fantastic.
Tom Cruise is humorous, but he really didn't sit well with me. He basically played Tom Cruise playing Tom Cruise playing a studio suit. He was so in on the joke and it felt so forced sometimes that it fell flat at times.
If you're going to make fun of yourself, do it in a way that doesn't feel like you're forcing it. Tobey Maguire's cameo, which I thought was the funniest thing in the whole damn film, and Jon Voight's were great examples of this.
Also, I felt Nick Nolte was totally misused. He was kind of irrelevant.