I'm enjoying this season so far. I like the monsters and the hunting. My only problems are 1) lack of Castiel and 2) now that Sam's soul is back, he's back to his whiny, kicked puppy look. I rather enjoyed him having a bit of a harder edge. I thought this week's show was so funny when Dean discovered that Sam was getting all the action when he was back in town.
I think we're going to have 2 story arcs - the mother of All (I think she's more than just the Vampire mother - I think it's all monsters) and the cracks in the "wall" that Death made to protect Sam from his own soul.