First, I liked this movie very much. But, as you can see from the previous comments, this is a movie that you'll either love or hate. But its hard to be indifferent to it. Zwigoff does a wonderful job of setting a mood that allows you to examine an artist who is depraved, perverse and, yet, insightful.
Everyone seems to come away from the movie with an idea that Robert is spared the obvious insanity of his two brothers because of his art. But I see it differently(hence the title of this comment). Even Robert admits that his brother, Charles, was a better cartoonist. Another way to view Robert's "success" and his brothers' descent into "crazy" is fame. Crumb was an involuntary icon of the 60's. Where would Robert be today if he wasn't recognized and rewarded in the 60's? If Zap comix had turned him away for his misogynist and racist comics, would he have had the subsequent female relationships that seemed to normalize his existence? What would his fantasizing over a high school yearbook and habitual masturbation meant if he was an unknown sharing a room with his brother at Mom's house?
When I watch this movie, I am always mindful that Robert's obvious genius would be lost were it not for his luck at being discovered. I suppose that is an obvious statement but, in Crumb's case, fame has managed to gloss over many unacceptable characteristics. And, maybe, that's not such a bad thing.
The film lightly touches on Crumb's relationship with his son and daughter. For some reason, Crumb's bumbling attempts at affection with his children were a bit disturbing. Or maybe its just that Crumb's fixation with wrestling and piggyback riding lingers in your mind when he hugs his daughter.
On a lighter note, I've noticed that no one has mentioned the soundtrack of this movie. Designed to be in keeping with Robert's love of old American music, the music helps to define the subject. I wonder why Zwigoff made no mention of Crumb's Cheap Suit Serenaders band.
Crumb comments against the crass commercialism of America. And, yet, I first saw this movie at a theater in Baltimore where the lobby was chock full of Crumb comic picture cards, mugs, etc.
Crumb, the movie, is a crazy world of contradictions and well worth the ride.