I think finding Jon Snow a girl and them having sex was the worst thing they could do to the character. It not only feels a bit forced, it's missing the point of where the character can go, given that audience is not crazy for the girl as well. Hey the giants look cool, why can't we have more about the giants beyond the wall or whatever. And plan some actual evolution for the character.
Jon Snow originally seemed like one of the characters meant to, nay, designed to, be able to connect particularly well with the audience among many characters that don't really do that (and at first I thought it was too obvious). But not only he's had very little to do, his interaction with Ygritte isn't really making the character evolve and so far it feels like the typical Avatar plot that I hate (up to and including the rival tribal member). It's the mix between the odd writing and the actor himself. An alternative could have been making Ygritte a slightly different character who doesn't quite get this far with Jon Snow and falls to her death climbing the wall. That would feel more like GRRM seems to like it. Or at least the parodies of the guy.
At first I thought Jon Snow could become an interesting character but his random drift through the show is a bit disappointing, specially since he's one of the characters in the single most interesting location.
"Why is Alice Eve in her underwear, gratuitously and unnecessarily, without any real effort made as to why in God's name she would undress in that circumstance?" Lindelof responded. "Well there's a very good answer for that. But I'm not telling you what it is. Because... uh... MYSTERY?"