I'm not sure why director Chodorov spends the first part of this movie talking mainly about himself. First he lets you know he's an experimental filmmaker, and when he mentions other, more famous, filmmakers, he talks about them in the context of what they meant to his own works. Perhaps he felt it was necessary to explain why he wanted to make the movie, or to give some context as to why these filmmakers were significant, but it's like telling someone about the time you met Hemingway and then spending the first 15 minutes talking about the book you're working on.
Just as I was about to give up hope there would be any sort of documentary at all, Chodorov got down to the business of talking about other people. While he briefly discusses works throughout the history of film, he is mainly focused on a few New York experimental filmmakers.
The movie is a mix of interviews and clips along with some general context. I'm not big on underground cinema (although I did like the namesake clip, Free Radicals and the works the guy who did the Gilliam- style - before Gilliam - cutout animation), but if you are, clips tend to be generously long, letting audiences fully appreciate the works. The interviews are generally interesting.
There isn't much shape to this movie, as the director feels letting you hear the filmmakers and see their works is all you need. The closest thing to a them is that experimental film making is the least lucrative art of the avant-garde.
If you're really interesting in the subject, or you don't realize that you would be fascinated by experimental film if you just saw some, you'll probably really enjoy this. But while some documentary makers can bring any subject to life for any audience, that's not the case here. How much you like this will depend a lot on how much you want to like it.