What I loved was twitchy!Cas. Misha Collins has to work to show that level of emotion without it being on his face. (and thus, I love him. =])
Jensen and Misha play so well off each other. I adore their scenes because it gives a new emotional depth to the show. The struggle between the two is so heartfelt, because Dean is trying to figure out his place in the world and Castiel is trying to figure out emotions (thus setting us up for what look like a fall).
And this scene was classic. It was suppose to be terrifying but Castiel/Misha's face! Let me explain.
"If anything threatens a prophet, anything at all, an archangel will appear to destroy that threat. Archangels are fierce. They are absolute. They are heaven's most terrifying weapon."
"These archangels...they're tied to prophets?"
"Yes."
"So. If a prophet was in the same room as a demon -"
"Then the most fearsome wrath of heaven would rain down on that demon. Just so you understand, why I can't help."
"Thanks Cas."
"Good Luck."
Subtext (or at least as I read it)
"I'm not doing anything wrong! But these dudes would totally take out anything IF Chuck is in the same room with Lilith *hint hint nudge nudge*!"
"Why are you doing this Cas?"
"Because I'm not as big of an unfeeling ass as you think I am. That's Zachariah."
"So, get the drunk writer in the room with the bitch -!"
"I didn't help you come up with it, but yeah, she'll buuurrrrnnnn! And don't tell anyone I helped you. And no one better have been listening to us!"
"Dude, if this wouldn't constitute as a chick flick moment, I would KISS YOU!"
"Please don't."