I just recently found out about this movie and have watched it many times. I vaguely knew who Buzby Berkeley was before, and my opinion of him was BFD. But after seeing the film I think he was undoubtedly a genius. The whole thing with the 64 white pianos that come together like a puzzle, all culminating in a scene that only lasts a couple of seconds, of a beautiful girl on a stage, is just amazing.
Like most movies, it's not entirely without fault. But large parts of it are absolutely perfectly entertaining.