Ooh, another one of these things! XD Spoilers, so on and so forth. :)
So, of the four shapeshifter-centric episodes in Supernatural, this one is my least favorite---but only because the other three deliver me some of my all-time favorite side characters (Ronald and Victor in "Nightshifter", Jamie in "Monster Movie", and Bobby John in "Two and a Half Men"). In other words, this episode rocks my socks away, because holy fuck, but I think my favorite 'monsters' in Supernatural may in fact be the shapeshifters.
Can we talk about how much I love what Supernatural has done with shapeshifters? Because I really, really, really love this show's spin on them. Excluding the one in "Nightshifter", most of them actually have personalities and, you know, are characters, with (heartbreaking) backstories and feelings and motivations and fuck, but I adore them. And as they go, this shifter in "Skin" can't compete with the likes of Bobby John (who I swear is like the biggest thing on my Want list) or the Dracula shifter in "Monster Movie" when it comes to my love, but it's still one of my favorite monsters in season 1, and even when the whole series is taken into consideration, it probably doesn't slide too far down the list.
This is also the first episode since "Dead in the Water" where we get to really peel back a few more layers of the onion that is Dean Winchester, and, well, Lord knows that I'm always up for that. ^^
This episode was written by John Shiban.