There's a lot of violence and drugs in this movie, but not as much obscenity as in Deadwood.
The reason I have some doubts is that the voiceover was done by the leader of The Dandy Warhols and he was also executive producer for the movie. He does say that the leader of the other band wrote wonderful songs and knew how to handle music like nobody else did, but that he was too violent and self-centered to work with (at one point, he insists he's god). I was surprised that some folks associated with BJM were listed as recording artists since I'd never heard of them.
I would only recommend this to someone who is strongly interested in this era of music and the bands involved.