The director's cut of this flick does some significant hand-holding, which is why I prefer the original. I've seen this movie quite a few times and what I took out of it was this:

It's a Wonderful Death

Or, how much better could life be for others without me in it? In a move that can only be called magnanimous, Donnie exchanges his life for his girlfriend's.

Good flick and unfortunately, Richard Kelly hasn't yet come close to repeating it.

I thought this movie was great. Full Disclosure, I didn't know it was a Richard Kelly movie until half way through when I imdb'd it out of sheer wtf-ness. I thought it was some kind of comedy version of Von Trier or David Lynch.
Not to say that it didn't make ANY sense though, i thought the casting of the Rock and various icons of L.A. superficiality (Buffy the valleygirl, JT, etc) was nice, and added to the feeling of airheaded people taking themselves VERY seriously and not having a clue what's going on.

Also, This.

I can't put into words either: how good this film is, or what it's about (this Sift will give you a better idea!)

The Donnie Darko Directors Cut is better (includes the bits Richard Kelly was forced to remove by the studio for time reasons).