I've just seen "Tropic Thunder" this week, and to put it short, it was pretty good. The comedy was great, the action scenes were fun, and the "The Fattys" and "Simple Jack" scenes almost put me to tears.
Though I felt Robert Downey Jr. was great, I just find his accent to be hard to understand. I think it's supposed to be not understandable, but whatever, I was just more focused in the Hollywood parodies and the goofy adventure these guys were put in.
So i'd say go see it, and I hope you get scenes from this movie in your "he..." I was going to make a reference to a Simple Jack scene in this movie, but I didn't feel like spoiling it.