This episode was the payoff (spoiler) to the whole Jimmy storyline as he really gets his revenge on Don. I stated in the last review it looked like Don was about to be caught, and I was right. For the first time in the show, his wife now has an inkling about her husband's double life. (hence the flashback to when he sold cars and was called out by a woman who knew he wasn't who he said. It paralelled his new double life of being unfaithful)
I thought Jimmy was annoying, but his turning his smiling persona off to vent then turning it back on after telling Don's wife about his knowledge of Don's affair, then dumping on Don, was really well done.
Jane was fired but got her job back after appealing to slater. I believe she will regret that decision as Slater is not one not to take advantage of that situation. (as Joan knows very well, which is why I think she dropped it after she found out how Jane was still there)
The show's showing the different mores of the time was again highlighted by the Sal storyline (closeted and repressed gay and the casual attitude towards littering. Many of the comments on this episode were shocked by it, but people did not really care about littering until the late eighties or so. (when I was little, my dad often casually threw trash out the window of his car..lol)
I believ Betty is about to act on some of the offers she had from other guys throughout this season now she knows that Don's cheating. I also agree with another on here that Duck seems to be careening towards a bad end.