Amazing episode. I wonder if Betty will take the lawyer's advice and just try to carry on with Don ... at first I thought she would leave him, but his explanation to her was so moving and honest, by the end I thought surely everything is now fine between them! As he said, in a way, nothing has changed. I found myself accepting that he did no wrong, really. I'm sure others will disagree.
His repeated infidelity is a far more serious thing, surely, and it was implied in Betty's conversation with the lawyer (when he asked if she could divorce him on grounRAB of adultery) that she has never been sure of his fidelity, but puts up with it.
By the way, I know this is a dumb question, but can anyone explain Joan's smashing a vase over her husband's head?