Uh, it's perfectly possible to be a sociopath and also do good and important things.
The personality part is interesting because it shows that Assange's personality is both what enabled him to accomplish all he did with WikiLeaks, and what sabotaged his efforts to make WikiLeaks into something even bigger and more powerful. His fallings-out with other WikiLeaks people predates much of the external pressure. Based on many sources, he strikes me as a deeply flawed individual who has accomplished great things. It's sad that he has not been able to accomplish more.
My guess is that history will show him as paving the way for Snowden and other future leakers. He'll be remembered more for the way his actions changed the discourse and environment for transparency than for his actual technical accomplishments. His personality will be an afterthought.