"The Future" (SPN 12.19), on the other hand, definitely wasn't. I always go into the myth-arc episodes knowing that they're probably not going to be my cup of tea (I'm a monster-of-the-week gal, through and through), but this kept me engaged throughout. Everyone's actions flowed fairly believably from their underlying emotional states, and there were some nice character details. Lucifer felt properly creepy, Sam used past experience to come up with a clever idea, Dean got to display his mechanical know-how, and Cas--well, none of his actions really came as a surprise. Also, some of the visuals were quite lovely.
(Does anyone else have the feeling that this next bit leading into the finale might wind up clearing the decks a bit?)