very good ep: I liked the story of the 3rd Winchester and the different reactions of the boys. Sam seems to be happy to have a little brother and to help him to become an hunter; Dean, instead, seems jealous by the fact that John treated Adam as a normal guy, played with him, while with he and Sam he didn't show this kind of "father's love".
I was curious to know how the story ended, cause it would be strange to have a 3rd brother, so I wasn't surprised when they made him dead.
Actually, I have to say that, in part, Dean is right to be jealous: ok, John only wanted to protect Adam but he would have known that demons or other creature would discover about Adam and attacked him. So, it hasn't been right to treat Dean and Sam in different ways: it wouldn't have hurt to make them play a little more like every kids...

This episode was interesting in a very special way for me: the trio of brothers.

I think that it became clear that the roles between Sam and Dean had switched from Season 1: Dean desperately wants a normal life while Sam has become the obsessed hunter his father was.

Dean sees Adam as the kid he dreamt to become and Sam only sees the vulnerability his "ignorance" puts him in.

I do like the fact that we still see glimpses of John even if he's long gone!