Was this movie effective?
I guess the answer is kind of a mixed bag for me. On the one side - it did bring out the klutz factor of his personality. I didn't really know that the butcher was also a bozo. That was a revelation.
On the other hand, someone watching this movie without knowing much about Idi Amin to begin with, would probably conclude that he was just a nutcase dictator who bumped off some officials he didn't like, so big deal. I think the movie did a bad job of portraying his fundamentally evil/genocidal/bloodthirsty personality.
You can't make a movie about Idi Amin or Pol Pot without lingering over the holocausts they caused. Everything else is secondary. Even if they played the accordion really well.