I first saw the theatrical version of this film a few times and then the director's cut version came along which goes longer, questionably changes some of the music, but ultimately assists better with understanding certain parts of this complex movie. Each repeat viewing tends to uncover a detail that I had overlooked or didn't understand previously.
I don't 100% understand every detail of this movie. I don't think anyone does, I don't even think Richard Kelly does unless he has explained everything in detail somewhere that I have yet to discover. With that being said, I don't think you need to fully understand a movie to have a great experience with it and that is what Donnie Darko is, a great experience. It is a movie like no other with an intriguing story full of suspense, relatable teen drama and a musical score that suits the movie perfectly.