2. I totally forgot about how demons flinch at the name of God ("Christo"). I don't think that was ever mentioned or used again after this episode.
3. Twice in this episode, the brothers explain to each other something they already know, just of the benefit of the viewers. Dean tells Sam what an EMF meter is, while Sam tells Dean what the name of God in Latin is.
Some fans were hard on Sam for making fun of Dean's homemade EMF meter, but I think part of why Sam reacts that way is because of Dean acting like Sam doesn't know what EMF reader is. Poor Sam and Dean don't know about the audience and our need for information.