Horror, comedy, drama, social commentary, this is one of the most balanced episodes of spn. It is absolutely thrilling and not a moment is dull. The "monster" is probably the best one, the creepiest.
My only thing was that Dean as we see in the later seasons has a problem with alcohol, doesn't make much sense that he wouldn't be drinking, he even does at the end to numb himself, i guess it can be interpreted as doing something that is enjoyable....in anycase not a big problem for this pretty much perfect episode.