The good thing about Peggy is that she's learning to stand up for herself and demand her fair share. So far it's not at anyone else's expense.
I think Don will return to New York renewed, having taken the time for introspection and resolving some inner issues. But he took his eye off the ball at work though. My feeling is that the 3rd series will focus on power play at the agency and possibly wrestling back control. I hope the merger doesn't take place as we'll have Duck taking command, but I can see there are too many storylines there for them to resist doing that.
Betty has been taking it out on Sally a lot which has been painful to watch, but thankfully she softened a bit at the end with her and spoke to her more truthfully about her situation. She's such a sweet little girl; I hope Betty's attitude with her warms further.