This is the band that was fundamental in the foundation of the Seattle rock craze known as grunge. The music was and is interesting, the history of the scene is interesting. We experience Mudhoney's climb to success, their initial status as avatars of underground music, the major label grab and how it effected the band, their adjustment to (eventual) moderate obscurity with legendary status intact. All that is part of the documentary.
The members of the band and the people involved in their careers--producers, label execs, etc., manage to say very interesting, smart things in this doc. And there's enough of the music live (and otherwise) to get you in the mode of the band.
In short--excellent documentary, one of the very best on a "punk" band I've seen. Interesting, definitely.