What stands out about PDA, is that it is almost an entire episode of great one-liners. None of the one-liners are out of context or character, and they are all driven by two points, the first of which is Valentine's Day. Between the one-liners, were the great visual gags such as Jim and Pam finding that their secret sleeping space was occupied, the box, or Ryan's office. PDA explored the drama of office sex, and relationship, showing once again the lack of productiveness of the Scranton employees.
The other driving point was Michael and Holly reuniting. When the idiot couple found themselves on Valentine's Day, they became a nuisance to the rest of the employees, to the point where Angela turned into the voice of reason. But where things got serious, was ironically, after Gabe's completely inaccurate talk to Michael and Holly, thus reminding Michael that he was once again on borrowed time with Holly. But since he was able to declare his love for Holly, she reminded him that they could do things on their own terms, and not be subjected to what the company dictated.
Dwight: "Michael. Confession. I have done PDA in the office."
Michael: "Thank you."
Dwight: "I have had intercourse in the office."
Michael: "All right."
Dwight: "As has Angela."
Angela (at Dwight): "Dwight!"
Dwight: "As has Ryan. As has Kelley. As has Meredith. As has Phyllis. As has Darryl. As has Creed.
(Creed nods gently).
Dwight: As has Michael. As has Holly."
Kevin: "As has Kevin."
Angela: "With who?"
Kevin: "She goes to another school."