Now we're talking.
This is were Season's 4 streak of classic episodes begins. After a so-so start of the season we get the first good episode.
Jerry, Elaine, George and Susan set out to Susan's cabin Upstate for the weekend. Now, concerning the script, I believe there are two things here: one is everything concerning the Bubble Boy and then there's everything else. All around the Bubble Boy story is comedic gold. From the memorable parents to the Bubble Boy itself and the Trivia Pursuit game with George, everything works. Unfortunately the rest doesn't quite.
Jerry and Elaine's story line is kind of dull. Nothing really happens and it really isn't funny. Kramer's story is funny but it is too short.
On a side note I really like what this season does with continuity: from the The Pitch on, every episode has some sort of element that connects it to the previous one. Here we see Jerry's relationship with the waitress from the previous episode and Kramer smoking the cigars Susan gave George before. On a larger scale this creates a mini world around the gang's life and develops a much richer story along the season. They never tried that before or after.