That scene was incredible. And bizarre. Because Sasuke was so shocked and scared that he forgot to be an asshole, and he was just Sasuke trying really hard to do something that happened to be stupid and wrong. When he broke Naruto's neck, I think he didn't know how to feel--and then Naruto got up again.

If it wasn't in the manga, I think it was a good addition--it's a scene I'll never forget. (And they left it so ambiguous that if it turns out that Kyuubi's not supposed to be able to heal a broken neck, they're not held to it.)