People are complaining about Alexis' acting in this episode, but I thought she played a manipulative imbalanced sort of girl just right. She certainly gave me creepo vibes. Her and Pete can creep out together.
Favorite moment was Peggy's PIZZAHAUS!
And I think, beyond the symbolic connection to Don's fantasy dropping out, the elevator shaft is part of the show's growing theme of existential dread, something that was becoming common in works at the time.