Last season they kept saying they were going 'back to basics' with the Winchesters. It wasn't until this episode that I actually felt that. Granted, most of it was the glorious reunion of the guest stars, but we also got a stand alone episode with a plot that hasn't been done before on SPN.
I loved the parallel between Sam & Dean's trouble communicating and the witches. I also loved that they showed neither witch was necessarily an evil being, and in fact saved the boys twice. Loved that, and I'd love it even more if, in the future, the boy's needed a witches expertise and called up one of these two. Not that I think that would happen, but I can dream.
Great episode overall. Really, the only thing missing was Cas and this is the first episode that didn't feel like it had a gaping Cas-sized hole in it.