I was pretty put off by the fact that so many main characters were done in in the first season. Had I read the books, I would probably have stopped after they killed Eddard Stark. I know that makes for a dynamic storyline, but that made me sad. I love Daenerys, though. Wonderful character.

I won't ask what they changed, because that'd spoil stuff for me if I go back and watch the second season at some point.