This is like one of those longitudinal sociology studies. See Frank at 20 something - see Kim at 20 something - now see Frank at 41 etcetera.
It seemed like during the reunion tour and all the way through the film that no band member had any real insights about what was going on. Perhaps some things are better felt than over analyzed.
It was clear that lots of audiences really liked the reunion tour and that there is some "magic pixie dust" around the band. Even if it still seems a bit mysterious to outsiders.
Music appears to be one of the few areas where you can relaunch a (product) band if they were ahead of their time / out of sync as Pixies seemed to be first time round.
I enjoyed being able to check the phenomenon that was Pixies and see how things have changed / what might be different.
I did see someone asking why there were no obvious outside commentators (pro & con) for the band. In my view that is what wikipedia and the web are good for and some of that can go on a DVD as a side bar.
I think this film was good because it allowed us to get a glimpse into the music and the band without talking the subject to death.