Just saw "Tropic Thunder" last night, and it was definately worth my couple of euros to go to. There's quite a few chuckles in the first 20 minutes or so, but it isn't until what happens to Steve Coogan happens, and then you laugh out loud for quite a long time indeed.
And Tom Cruise is awesome in it. If he's planning a late-career turn around, he's executing it rather well. Since Collateral he's been great in movies, as opposed to just bland. Or just being himself.