Well. Interesting.

This ain't hell.

John has been retconned. He's coming in after All Hell Breaks Loose, so he may or may not have come from heaven. It isn't like he's going to remember anyway; he just knows he was dead.

No previous girlfriends, no stupid drama bullshit. Sam, Dean et al, feel free to tell him he was here before, but he won't remember any of it.