Well, I've read loads of reviews and criticisms concerning the plot holes of the 19th episode of latest season Supernatural & although I think Brad Buckner & Eugenie Ross-Leming did not do their home work, this episode is not that far irrelevant from the canon.
This episode is mostly about the second trial regarding closing the gates of hell & Sam has to rescue an innocent soul from hell unto heaven according to Kevin. Then the Winchesters get hold of a crossroads demon and informed of a rogue reaper who can make a way through hell & back.
Now, reapers can be a sort of angel as they worked under Death the horseman (The big daddy reaper, the angel of death in lore from 'Abandon all hope'). So they can easily know the location of purgatory as Castiel rescued by many angels. So Ajay can easily hack into Angel radio & know the secret. Before season 6, Castiel & Crowley, how hardly they tried, could not know the unknown location even if they got hold of a rogue reaper. Now, for example, many top level angels know the location but not Crowley (unless he caught one of them and found their "factory settings"). Also reapers cannot be seen by someone other than dead but i think Ajay (like an angel) take a man's consent and ride his vessel (That's why Ajay exclaimed when Sam and Dean called him by his reaper name)
After that, Sam can find Bobby's soul so easily without that much of an effort. I think as Ajay is the reaper who send Bobby to hell, he may have tipped Sam on their way. Also 1 hour in topside may be 120 hell hours. So Sam has plenty of time. I also think Naomi has her way in this situation as there were not so many demon guards around to harm Sam ( only my speculation).
Sam cannot recognize hell may be because he was in Lucifer's cage, not the original hell. There may be different hells for everybody because we have seen three of them so far (the final of season 3, the long queue in 6x20 and this dungeon like hell)
Before season 4, Sam could not find a crossroads demon and thus a rogue reaper to save Dean because probably there isn't any. May be rogue reapers/angels (rogue angel Balthazar?)were not there before chaos in heaven( after season 5). And also as we all know the angels had their hand in apocalypse. So they wanted to jump started it by breaking the first righteous man & did not make it an easy task for Sam to rescue Dean back then. We also informed back then that many angels died to rescue Dean but that can also be a trick of Zachariah( he has his hand in killing many angels to break a seal).
After season 5 both heaven and hell is a mess now. As for Crowley, as sinister as he seems, he cannot make hell as creepy as season 4 because there were plenty of major demons out there (Alastair the picasso with razor, Lillith herself & maybe Crowley) back then. Crowley can be plenty sloppy & can not control all the demons as the new king of hell (It's only my opinion). Bobby is also not the prime target of major demon Alastair or Lucifer, so he can take the tortures of hell pretty easily than the Winchesters even after 120 years or so.
Benny does a huge favor for Dean & let himself getting beheaded to rescue Sam ( The same little brother who wants to kill him!). He leads Sam & Bobby's soul to the purgatory-earth portal (so easily because he knows the exact location) & decides to sacrifice himself. The goodbye scene between Dean & Benny is one of the high aspects of the episode (Mostly because of Jensen Ackles Seriously, what do they find in that Homeland guy, did not like him in 'Dreamcatcher' either).
Now, the writers can use this an opportunity to bring back Adam but that can only be possible by Death, not a possible task by Sam who has to complete the trials. Bringing back Bobby again & again may be a faulty decision but who can judge the boy's life in simpler way other than Bobby? They cannot find his replacement yet.
I am bedazzled by the ending as I cannot decide whether actually Crowley kidnaps Kevin again or it was just a mind trick by Naomi (She can enter the safe house) . By glass shattering I like to assume it is the work of an angel because Crowley has no reason to clean up the mess. Kevin's paranoid visions creeps me out though. Who says the show is not scary anymore?