Not particularly fussed on this film but I can understand why it is thought of a classic.
The scenes from where Sheen sets out to find Kurtz until he finds him are excellent with the helicopter attack being a cinematic moment.
I actually thought Brando ruined the ending by obviously being grossly overweight and not wanting to show it and being a ham by talking drivel.
It's is a shame that the original ending was not used or Brando replaced as it would have seriously enhanced the movie.