The differences between the books and the series are more dramatic in the second season, Riverrun, Brynden & Edmure Tully and Meera & Jojen Reed being rather glaring omissions. I hope they don't keep that trend going as the series continues. I realize they sacrificed faithfulness to the book in Arya's story to make Tywin Lannister an actual character rather than just this looming shadow, but it's surprising for HBO to be going to lengths to tone things down and soften them up, considering how Arya deals with Harrenhal in the book, which was more interesting in her development as a character.
While the second season fell short of the first season as a quality TV series, it still wasn't half as bad as the book. Clash of Kings was a gigantic drop in quality from Game of Thrones, and GoT was nothing particularly brilliant anyway. I can't imagine how the subsequent can get worse, but the internet tells me the quality drops as the series goes along.