It wasn't Pluto who had the tablet, it was Plutus (or Ploutos), the Graeco-Roman god of wealth, which the show turned into the god of greed.

I want to know what the boys did with Mjolnir.  That isn't the sort of thing you want to leave lying around, and the fact that Sam could wield it so effectively makes me think they should have hung onto it.

 This was a good ep, though it felt like Mjolnir was too much of a tip of the hat to the Avengers.

The humor felt less forced than some of the other recent eps too.  

The tablet's an interesting MacGuffin, but how much do you want to bet it turns out to be a manipulation by Crowley, and some kind of trap that unlocks the cage or something like that, leading to...  /*drumroll */ a cliffhanger ending...

Quite right...Plutus.  and I wondered the same thing about Mjolnir.  Sam offs a couple of demons with it..or whatever the old guy was...and then next thing you know you don't see it again.

was that loki trying to get mjolnir or thor?

ya know that was a pretty small bag for 5/8 of a virgin.

 Loki was really Gabriel.  One site said the old guy trying to get Mjolnir was named Vili.  I really hope it wasn't Thor, because I think they could do something a lot more entertaining with the god of thunder than have him be a background character that gets offed so off-handedly.