I've been generally pleased with this season so far. Clash of Kings would be a hellish book to adapt, IMO. Game Of Thrones has a much more straight-forward structure, so I was a bit harsher on some of the deviations. So far though, Season 2 had a slow start, but now that it's kicked into high gear, it has been excellent. The changes to the book actually enhance the story and feel much more natural than before while in Season the additions usually amounted to either Ros fucking someone or two characters chatting about something.
So yeah, big thumbs up from me for Season 2 so far. If the quality keeps on going up like this, Season 3 is going to result in a lot of spooge-covered televisions.