The Stannis scene was kinda painful but I don't find his characterization on the TV show substantially different from the books. He definitely has this period after his defeat at the Blackwater where he basically does whatever Melisandre says. She very much caused him to drift away from the principles he holds so dear in both occasions.
I am a little jealous of those who hadn't read. Not only did things happen so much faster on the TV show which made it more shocking, but the actual event was more traumatic. Then again, considering I tossed the book and didn't start back reading for 2 days after I finished that chapter, maybe it's best my TV wasn't in danger.