I think you answered your own question. The touch pad seems to be mainly used as a button, unless it's a first party game. I know some games let you scroll around maps with it though, maybe destiny will let you do that? I'm not in the alpha.
@machofantastico: Just so you know, GR and Uncharted have been on Vita's PS+ for a while now and probably still have a couple months left in them before they get swapped out. Also, Vita Uncharted sucks pretty hard, but GR was fun enough.