I've been rewatching season 1 and I saw something I missed before.
Shortly after Don "caught" Roger coming on to Betty, he got into the elevator and started talking to the operator while peeling some bills off a roll. The door closed, and nothing was heard of the conversation. Later, he and Roger are lunching on martinis and oysters, before their big pitch meeting to the Nixon folks and Don seems uncharactoristically (for him) cagey. This segways to the broken elevator and 23-story stair climb and Roger famous hurling scene. As Roger sits on the landing, Don asks if he's ok? Roger says fine, and Don turns away with a satisfied smile on his face.
I guess I'm a dunce, but I didn't catch this before. Don set Roger up! There was NO broken elevator! Revenge is sweet and secret.

Yes, that is definitely what he did.

One of the cool things in that scene,  Don kept reordering drinks and oysters and Roger kept eating and drinking while Don nursed one drink and just watched...
 
What a contrast to Rogers reaction when he thought he caught Don coming on to Jane.  Roger has no finesse.

Don will of course find a way to win this one also.  If perhaps  Conrad Hilton shows up a S/C and asks for Don.....

Revenge is a dish best served cold

There's been talk about Sally perhaps not being Betty's (or Dons) biological child. I'm not sure what's up with them, but it made me recall the scene in Season 1 where Betty did her low-speed crash into the neighbor's outdoor fountain. She said something to effect that if Sally were killed, she could eventually live with that, but if Sally had received a scar, and was "disfigured" for life, she would never forgive herself.
Is this just the former model talking, or someone who really doesn't love her child?

Speaking of Sally,  I think it was season 1, when the dog attacked the pigeons, Sally was crying.
Later Betty said something like "I'd like to have a picture of her crying".  Weird?

I don't quite feel that Sally isn't her child.  I think Betty saying she couldn't bear leaving Sally with a scar on her face was just indicative of the times and how she herself was raised... look good to get a man.  (Although, as Betty said to her psychologist, "then what?")  I'm not sure why she would want a picture of her crying, I thought she said it was pretty or something... but maybe that's more indicative of the kinds of emotions Betty reacts the most strongly to.

I remember - I thought Don also ordered more rounds of martinis and oysters with Roger?  Didn't Roger make a comment about how he knew Don could hold his own?  Good point though about how differently Roger handled Don and Jane.  I forgot about the other incident, but you're right - Don is much more gracious up front, and calculating in the end.  Roger is just a buffoon.