I saw this movie years ago when I was a child and it has never left me. I was a firmly entrenched Christianity at the time, but now I am a confirmed Atheist. I believe this movie helped to lay a foundation for my eventual realization that the mystery or God is founded in the need for absolution and comfort rather than any rational concept as Capt Cutshaw comes to realize. I am truly grateful that "Twinkle, Twinkle Killer Kane" (the title I always knew it by) started me on my path.
As to the actual movie, I have seen it several times and remarkably the dialogue and story holds up. The direction could be a little heavy handed at times, and the editing is a jumpy, but well worth a late night watch. Again though, I found it to be metaphysically profound about the age of 12. Don't know that it would be as substantial now. Lastly, Stacy Keach is phenomenal in this role. He has been sidelined in much of his acting career and his talent has been under-appreciated, but in this movie he portrays an impressive blend of perfect blank affect coupled with sociopathic undertones. This is how Hannibal Lector should have been played in "Silence of the Lambs." This movie is worth a watch for the humor alone, but also worth it for the esoteric idealism.