I liked this story for all the reasons others have mentioned, and Varda's comments added another layer to my understanding of the story. But this story didn't sit right with me. As I read it, the dragon didn't escape his fundamental nature - the dragon could only acquire the knight's ideals because the knight took on the dragon's evil. The capacity for personal development is central to my understanding of the world - well, at least my acceptance of the world - and instead I read this as a story set in a world of zero-sum goodness - dragons are evil, knights are good, and the only way a dragon can become good is if a knight falls as well. Perhaps that was not the author's intent, but that's the only way I can parse the sudden inversion of these two characters' natures.
For those of you who have watched the entirety of the Dexter series -
This is pretty much the same issue I have with its ending. I thought Dexter was changing and realizing that he wasn't a monster throughout eight seasons, but at the end it felt more like "a leopard can't change its spots." Meh.