I don't think he is. I spend too much time psychologically analyzing characters and I'm quite sure a lot of his SHOW of arrogance is just his way of compensating for feeling inadequate underneath. Plus he's really subtle about it but he's shown that he really cares about Helen - I mean, he was willing to get himself blown up by the particle accelerator in "Animus" so she could escape, and in season 2 he knew the ray gun he made to fight the Cabal wouldn't work unless he made it fatal (which would've killed Ashley), but he didn't do it until Helen specifically asked him to. Obviously I think in some part he is kind of full of it, but a lot of it seems like a way of preventing himself from getting emotionally hurt. In "Sleepers" he practically had a breakdown because being a vampire was the only thing that made him feel special
Then he found out he could pop buttons I do have such a soft spot for Tesla and I do think he is a big cuddley teddybear really. But I also do think that I would end up slapping him silly if he was the petulant child he is with Helen sometimes. D'aww, I wish I could give him a hug when he becomes devamped... I still think he could have come up with a better name than the 'Devamper'. I loved Sleepers, it was a particular favourite of mine. *sigh* I need my own personal Tesla to cheer up and be cheered up by. And quite possibly drink rather expensive wine with.