I would completely LOVE it if it turned out Dean was still in hell and all of this is a false dream. (And I sincerely hope that Dean's faith isn't the only major theme of S4, though I am enjoying the exploration of it so far).

I never thought about the Colt and the knife taking their souls, just their mortal lives.

Well, I guess I had always just assumed that something kills demon souls, it will kill human souls too. On the other hand, the knife didn't kill Castiel, so maybe those weapons are specific to demon souls. (Which just leads to the question, how are demonic souls *different*? Is it something like was implied in Buffy about soulless demons (at least in seasons 1-3, before Joss complicated the mythology) that past a certain point demons no longer have free will, so they're necessarily evil, and the weapon can actually distinguish that? It makes an actual difference in soul composition?) A Catholic explanation might be that damned souls lack the grace of God (grace being literally defined as the divine light within a soul), so perhaps the weapons can't work on a soul with divine light? Or something else?

We need Kripke to come to a fan con so we can grill him on these important questions!