Synanon actually still exists through its German branch. When I lived in Berlin, I would regularly see Synanon drones moving boxes in and out of people's apartments. I think the movement has monetized its adherents and put them into forced labor...much like Scientology. I don't think they're putting snakes into mailboxes anymore, but they're still creepy. One of the guys jumped out from a dark alley and yelled at me for buying beer one night on the way home from the grocery store.
I was a little underwhelmed by Going Clear as a documentary, but the book was superb. I would like to see a documentary just on the life and psychoses of Miscavige.