Eh..... I'm not entirely sure what that was about, but "Defending Your Life" definitely wasn't a normal episode of Supernatural and not in a good way. Although I liked the scenes with Jo, the episode tries to aim for something complex and misses, generating a patently artificial situation which feels unnatural and forced.
The central motivator for the exploration of guilt is the Egyptian god Osiris randomly popping up, and he's a one-note character bent on carrying out his form of justice. Again, Jo and Alona Tal are awesome, but it's a quite arbitrary what Osiris does and this allows the writers to create any dialogue they want without fully addressing the major issues of the season.
But there are a few worthwhile things to come out of the episode--Sam revealing that he has no guilt, in great contrast to Dean. Trying to quantify amount of bad things each brother has done won't go anywhere, so it's best to chalk it up to mindset. Sam doesn't really care what he's done in the past while Dean still carries the weight of each action.