At the beginning of the season, Penny balked at dating Leonard, thinking she wasn't smart enough for him. It was good to see Leonard take a stand in this Christmas episode, after Penny dates Leonard's smarter, cooler colleague (Michael Trucco).
I also enjoyed seeing what presents Penny, Leonard, and Sheldon exchanged. Presents can convey the closeness of relationships and how well we pay attention to each other at non-gift-giving times of the year.
Finally, I was pleasantly surprised by this episode's longer-than-usual tag, appropriate to the gift-giving.