I haven't read a single thread on the Double Fine Adventure forums. Should I? Will I miss any of the rewards if I don't go there? I don't really care about having early access to the game or documentary -- like Toblix, I'd prefer to experience it all when it's polished and released.
There's one thread that you should follow, at least. This one:
Also: The documentary is being designed to be spoiler free, and it's brilliant so far. Well worth your time.
Note: Episode 2 of the documentary isn't posted there yet. Not sure why.