I don't know if this has  been said before, I didn't see it on the site :)

But since I can't get my torchwood fix till (hopefully) next year, I have been rewatching(via youtube) and rereading recaps of old episodes. I read through Kiss Kiss Bang Bang and the office scene between Ianto and Jack was so adorable. I focussed probably a little too much on the Janto parts (but don't we all?).

To me it seemed like the kiss in episode 3 marked a turning point in the Janto relationship. Since the first episode Ianto had held Jack kinda at arms lenght. He got a little snarky with Jack(and the rest) in episode 2 and in episode 3 they had "the talk" about Jack leaving. I think that scene was meant to showcase that Ianto was taking the steps to let Jack back in, to trust him again after what had happened. 

But those are just my thoughts :)