With Nathan, I think, part of Peter's effectiveness arises from the fact that he hero-worships Nathan, and Nathan wants to be as good a guy as Peter believes he can be.

Oh, definitely. He is his External Conscience, the one who always believes in him (with Claire and Hiro being Supplements, obviously). I'm very excited to see what happens when (and if they'll have him survive that's very likely a "when" not an "if") Nathan starts to develop his very own *gasp* Inner Harddr Conscience.