The ticking clock is always a pretty cool device to implement. But I hate transparent use of obvious plot devices. This one is sort of like a complicated MacGuffin mixed with a pledge. I'll stop giving you wiki links, I spend days at a time there, I wouldn't wish that on anyone.
I was worried people wouldn't understand the last panel. It was a little abstract, but I wasn't sure how to describe it in the script. I always liked the trick from the Batman movies where someone looks away and he's gone. But Supernatural pushed it a little further, you'd see the character's response as they watched some Demon or Angel or Wizard teleport, but they wouldn't show you. That gave them the freedom to not rely on low-budget CGI or something to make it look realistic.
In any case, Adam's kind of a dick, right? But you'll find out why. Eventually.