This movie was fucking hysterical. I saw it last night. Myself and the audience were laughing throughout the entire movie...to the point where I couldn't even hear dialogue. Love the shots this film takes at actors and their motivation for taking roles.
Downey Jr. steals the show, pulling off a bunch of convincing accents in the process. Can't stand Jack Black but he was funny here. Another scene-stealer was Jay Bruschi, basically playing the straight guy of the group. I'm not a Stiller fan and I thought he was the least funniest guy in the movie. Cruise's cameo was great.
Noticed one scene in the trailer that wasn't in the movie. After Stiller's character is untied, he attacks his captor then asks if he hit him too hard, thinking it's still a movie. Obviously, his captor attacks him.