I loved this piece of writing! With every s4 episode and the whole Dean/Castiel interaction I've watched I found myself wanting a good fanfiction... today I finally searched for the pairing. It's hard to describe, but I think this ship is something special, not one where I would want to read PWPs or crackfics (and I came across them at first), because IMO that just doesn't fit. I think the whole point about their relationship is that it's platonic love, like you said; an angel with a body that's not really his and someone who is practically walking in a body that was dead. This is perfect, just like I would imagine them. Castiel observing humans and being so different from them, not understanding them at all at first, but growing to be more like them with each day.

"Dean’s lips quirk up into a brief smirk; a reaction most probably tied to the mere mention of the word “sex.” Castiel can understand why humans find the topic humorous; from what he has seen, it looks ridiculous." <- I loved this line. XD "Castiel’s vessel is currently undamaged, and yet he aches." This one as well.

The ending seems a bit strange to me, maybe because it's so short. I just can't imagine them going from their usual relationship to sex suddenly. But I did love their dialogue about the gender, it's so typical of them and just... in character.

I hope you'll write more of them =3