for me it wasn't that jon was sent north. i expected that as it had previously been set up.
it's that the night's watch serves no purpose. send the bastards there... to do what? what are they watching? if there's nothing to watch, hasn't their watch technically ended?
i'd prefer to have had jon banished from the realm or something and then he chooses to go live north of the wall.
i kind of think that's going to be the book ending and that he'll end up with val.
that part obviously couldn't happen in the show because she's not in it, so they wrote it as rejoining the night's watch which i just don't think makes sense.