Yeah, it was a strange one.
So what's the move now? Use the key to decode the demon tablet? I can't imagine the Winchesters passing on the opportunity to close the gates of hell forever with the key in hand.
.. But, of course, they'll have to worry about someone else getting a hold of it. I'll bet Crowley comes after it and tries to find the angel tablet.
"I don't know how to put this...but I'm kind of a big deal"