I liked what they are trying to do but the have some serious flaws with it.
1st being Sam was told by Crowley what happened to Dean.
And Dean knows how difficult it is to open a gate to Purgatory. 1st blood of someone from Purgatory (the easy part as their are Leviathans still on Earth) a ritual (which Sam knows or should, though he was a bit nuts at the time), and a solar eclipse.
THat last one is a little harder for a human to manage (not even Angels can). Those do naturally occur, and they occur once every 6 months or so. Thats to open a portal, one that stays open a few seconds.
How could Sam (after all they did spend a year with even smarter help trying to figure this out) manage this, keep said portal open, manage to find Dean through out Purgatory and get out?
The answer is he couldn't and Dean should utterly know this, as Dean knew he couldn't get Sam out of Hell (though admittedly he at least knew Angels could access Hell and did have an Angel friend. So him at least looking into it, made some rational sense.
And its something Sam absolutely should have used to defend himself.
Just with what we do know, the whole issue of Dean feeling abandoned by Sam shouldn't be occurring.
2nd. With what is happening to Kevin, not once do we really hear Sam tell Kevin, listen I do know what your going through. Even when Crowley kills his girlfriend, not once does Sam let him know that he knows what its like, he just keeps silent.
Now this doesn't mean Sam wont talk to him about it, but if it doesn't occur or isn't referenced, its a huge mistake on the part of the more openly caring member of the Winchester family.
3rd. Clearly this season's focus (and perhaps more) is heavily going to feature demons. And the show still will not even address Sam. Its insulting! Hell even for them to just say oh after going to Hell God took those abilities away (and we already know no Angel or Demon has the ability to remove his power, based on what we know only God or perhaps Death himself could). Or no mention that he refuses to use them, just because he's afraid what he might became. WHich frankly also makes no sense. We know Sam was specifically designed that his drinking demon blood would never harm him, even the terrible withdrawal's are short lived.
I hate it when the show just lets something, so integral to a character just disappear without ever addressing it. It would be if Dean or Sam went to Hell and after they came back they never once mentioned it again.
Besides those three things, and some extremely poor acting on the part of the girlfriend, I really enjoyed the episode, but so much of it is based on a faulty premise that it makes it really difficult to actually buy it.
It was nice to see a slightly larger visual approach to the story telling, in places, though its clearly still a low budget tv show.
Frankly its maddening. Certainly the idea of Sam jsut refusing to do it