I thought it was pretty good. It tried to present the myth of Gene in a more balanced light... some parts were compelling and some parts... meh.
Certainly well made and mostly interesting, but I would have like to have seen more from people outside of Star Trek that knew him. One of the best moments was when he interviewed a couple of neighbors about his dad.
But if you want a good doc on the Star Trek experience I would certainly recommend Shatner's "Get a Life." While it covers a lot of ground that was presented in the "Trekkies" movies, it really does a great job of discussing the overall mythos of Trek and why people are so attracted to it.