The Good of Tropic Thunder
It certainly was funny. The opening scene which actually are fake trailers was some of the best for me. Again, out of all of them, Downey Jr.'s trailer was the best. But I think it played into the film well because Downey Jr.'s character was supposed to be the top, academy-award winning actor while Stiller was supposed to be the action, B-movie actor and Black was supposed to be the C-rated comedian who once an A-lister (i.e. Eddie Murphy). I had some legitimate laughs through the film. I certainly loved the beginning of the guerrilla-style film when they think the director isn't really blown up and the people shooting at them isn't really South Asian soldiers.
As I stated before Downey Jr.'s performance was great. He played off the stereotypical black guy pretty well, which was great social commentary if you look into it further and plays rather nicely against the other, authentic black rapper turned actor (i.e. 50 cent/Ice Cube).
The Bad of Tropic Thunder
It was poorly written and poorly directed, I must say. This is one fault I had with its ridiculousness. The child chief/leader was not needed and even though the child was speaking a different language I can tell he was a terrible actor. Downey Jr.'s character's end was quite terrible as well. His turn from being actor to just being himself didn't annoy me because it was predictable but because it wasn't handled very well. It was so sudden and uncomedic. It would have been great if another character was getting through his mind throughout the film and at one point he breaks character. Everything about Tom Cruise's character as the producer was terrible. I couldn't wait to get out of that long and pointless scene. The end credits with his dancing was just as ridiculous and terrible.
Conclusion of Tropic Thunder
Wait for the DVD. It could have been great but it's really just ridiculous, over-the-top and poorly written.