The plot line is great, on one side we have Cas taking the reigns of leadership unwillingly and trying to find a mole in his Angel resistance.
On the other side we have Dean willingly taking on the burden of having the mark and beginning to enjoy his work. I personally love Dean for this gritty type of stuff, he's always been the badass of the show and this is his most badass episode.
Without going into anymore, Dean has The One Blade and goes H.A.M. that is all.