I liked the episode, liked, it certainly wasn't a classic by any stretch but it was a good episode.
I know several people are not going to want to see a story with Adam in it (as many hated the very idea of the character), but not me as the idea of John (let alone) Dean not reproducing seems extremely unlikely.
And I can certainly understand the use of the character, as both Dean and Sam (both have strong bonds to family), even one they don't know (plus they would probably do the same with a friend or a stranger), but only Adam gives them the illusion of having a host body.
Always wrap your lies with some portion of the truth it makes it easier to buy into.
My primary quibble (and its a reocurring quibble), is when trying to convince Adam that Angels lie, they keep not mentioning how the lies of Angels led Sam to start the apocalypse. I understand why Sam doesn't lay this out to Dean all the time (one he does fell tremendous guilt about it, and it''s not in his character to throw things in people's face), but a few times its very salient to the story. I do think Sam really should have at some point rationally told Dean why he believes the Angels that this is the only way, when he knows how much they do lie.
One might argue why they didn't bring John back instead of Adam, and I don't know if John would give in to the Angels wishes (meaning he would not give out his location), plus I think the angels would not want his influence on either of Sam or Dean. So it does make sense.
It was nice to see Dean finally tell us (and Sam) the full reason he thinks making the deal with Michael is smart, and it was nice that they haven't forgotten that Dean saw a world where Sam did give in (and he didn't). Though we know it, its good for the characters to see. Nice to see Castiel take a pound of flesh out of Dean, as I have been saying that he might have gotten attached to the guys his motivations are his own and if push came to serve he would do what he thought God wanted (even now I think this is true).
I really liked seeing the differences between Sam and Dean in this episode. Dean who has always been hesitant to truly trust Dean, and Sam who always wants to believe the best in Dean. Both knowing the good and bad in each other, and just how they perceive one another.
Then we have dearly departed Zachariah. His time and come and gone, I did really enjoy the teaser though with him, but his over the top performance in hell made him less a character and more a caricature. Sure it was only one episode (and really just one scene), but with so little time left on this storyline, it was very nice to see him depart.
On Castiel, again very nice to see him lose it on Dean, and both him and Dean gave some good moves (I especially liked the idea of Castiel making the sigils on himself (of course the Castiel girls are probably freeze framing on the second of bare chest, but oh well.
The thing I did think hurt this episode is that once Dean is back with the guys his sense of defeat seems utterly gone (now this could be due to the fact that he has come to a decision), but I wanted to see a little more bitterness at being held captive, either in his snark, or just being more sullen. That was the only acting problem I personally had (or even tone) for this episode. I did like the snark (as its general the humor that for me works on the show with a few exceptions both ways of course).
I keep saying that I wish Castiel would have died, and I do mean it. Not only to make the story more powerful (as he is a well liked character), but to remove him as a possible character for season 6. I just can't stand the idea of Castiel either as he is now or a fully cut off from angel Castiel who is human being part of a season 6. But hell I am also the person who would have loved to seen the boys get back to bobby's at the end of Abandon All Hope and find that Bobby had been killed.
It's supposed to be a milestone episode. They sent advance copies out to media. Reviews have been very enthusiastic. I'll have to watch it tomorrow after work. sigh
