I'm really looking forward to seeing this. Loner rock (to coin an annoying buzzword) has long been an interest of mine, and the Jandek mythos and music is absorbing. The movie doesn't unmask Jandek (and really, unless Jandek is really Lou Reed or something, what's the point?), but it looks like an interesting overview of the whole Jandek mini-phenomenon.
For those of you not familiar with Jandek, I highly recommend visiting your preferred file sharing program and downloading a few tracks. Basically, it's mostly tuneless acoustic music (neither the terms "folk" nor "rock" really apply). Jandek plunks away on a few strings or a single "chord" in no particular rhythmic or melodic fashion while singing in a mournful half-mumble, occasionally breaking into a higher-pitched yowl. The lyrics make little narrative sense yet somehow paint a vivid picture of despair and resignation. The overall effect is compelling yet more than a little disturbing - there's a sense that this was not meant for public consumption. It's almost like listening to someone's therapy sessions. (Of course, the real reason Jandek is so notorious is because of the backstory, but the music elevates him from being a mere curiousity.)