All shows eventually jump the shark at one point, Seinfeld, as great as it is, was not the exception, but there was not really one episode that stood out as saying, "Okay, the show is done, now." But this was pretty close.
I still laughed a lot during the episode. Jerry's performance while Mrs. Hamilton was flirting with him was great, and the four-way phone call, while somewhat childish, was still quality humor.
The writing for the episode just felt so beneath this show. It was the kind of thing George complained about in the one episode: it was dumbed down for a mass audience.