I watched it two or three times, and read the book, and I think what I find most interesting about it is the way it could conceivably appeal to both liberal/rebellious youth (anti-authoritism!!! Helping mentally ill guys go out and get laid!!) and conservatives who hate nanny states. Sort of like Patton appealing to hawks and doves at the same time. After all the book was written by a countercultural figure. And it's a crowd-pleaser that you could write about. But I've never ever been in love with it.
I think what I failed to "get" the most about the film is Nurse Ratched. I only understand on paper why she's such a terrible villain. She never made me hiss and playing her seems like it must have been a real drag, even though I seem to recall Louise Fletcher won an Oscar for it.
My favorite moment in the film is Christopher Lloyd going "blah blah blah blah blah!!!"
I can't remember much how the film deviates from the book....the Indian is the narrator in the book.