This is the episode where I really realized what a reliably brilliant writer Robbie Thompson is (that is, waching it when it first aired - now I'm just rewatching the whole thing...). This episode has such great emotions in it - the unbreakable friendship of Cas and Dean put to the ultimate test, the strange attraction-bond between Cas and Meg (Their conversation as he bandages her wounds is a memorable moment for sure), and once again Dean's love for his brother is well played.
And my lord, the banter in this one! Every word out of Meg's mouth is perfection (I always remember the Unicorn...) and the way Rachel Miner delivers those lines is just beautiful. It's episodes like this that can lift a side character to really being loveable and a fan favorite - even a demon! I think they managed that often on this show - Bobby, Cas, Crowley and even smaller parts like Charlie, Meg or Benny were given so much personality, and so well cast and played that we miss them too.
Love this episode.