I agree with much of this and see your points. I don't mind the shifts in Ianto's character, though. I spent most of last season bored and/or irritated by him and his angst. And it makes sense to me that the vast amounts of time this team spends together would have them rubbing off on each other -- in more ways than one --, enough that they would pick up some of each other's habits and characteristics, including Ianto becoming more blatant with his snark.

(Also, I disliked Beth and felt like her personal story was too much of a retread from ideas done not just on this show but elsewhere in sci-fi. I think part of my problem was with the actress, however, and everyone else seems to have liked her. ::shrugs::)