Interesting thoughts. Snowden definitely has some well thought out arguments in favor of his actions. I would guess he believes he is "just". My opinion is based on reading his voice and body language. It's hard to describe; he seems a little too pleased with himself and a little too happy to be along for the ride.
He may very well be vain (I haven't really picked that up myself, but I heard several people independently form that opinion, so that's plausible), but I don't think that's mutually exclusive with pure intentions.
