This fic did huge things to me. First of all, Dean taking care of hurt Castiel was delicious, delicious! The subtlety you used to show their deep feelings was breathtaking and refreshing, considering how much explicit stuff's out there.
Bobby, brilliant.
Soulless Sam was incredibly convincing and realistic.
The dark side of Dean; uncomfortable in the extreme, especially as I hate animal cruelty of any kind, but I see why you needed to use the device. It did succeed in shocking me, and the unpleasant truth that Hell "reveals" a person's true self was profound.
I hated what Dean did and his reasoning, but I was so impressed that he would become that dangerous in revenge for Cas.
I would much rather read a complex, dark narrative like this that a bright, shiny, sex-orientated fic. To me, it shows deeper and more committed feelings and somehow makes much more sense than a roll in the hay ever could.