Pretty well said Szlia. Don's unhappiness with his wife
This surprises me. Siz and I discussed this at the end of Season 5 (Disagreed

)--Megan's transformation at the end of Season 5 into a more superficial, self-interested figure and how it turned Don off, completely. Given Megan's actions last season, I'm surprised why people don't see why Don dislikes her. Everything he based his initial attraction on was completely wiped away by the end of last Season.
She's great with Children....Then she doesn't want any and becomes
annoyedwhen they are there.
She's interested in Don's profession.....She's not and has
alwayswanted to act (She just NEVER mentioned it before??).
She's self motivated and reliant (Independent)...She throws a fit when Don won't use his influence to unfairly get her a part. (Not to mention using his money for classes, extra time for auditions ect--rather than working during the day and going at night, or weekends. The show makes a point to mention this, when her friend talks about how Megan can stay at home all day and practice, without worrying about the rent ect.)
Megan sold herself to Don, she advertised herself as something she isn't. Don abhors that. That's why he's always had such a powerful self loathing, because he's always had to do that. He's always been happiest when he can drop the Don Draper routine and be himself (California--remember when he wanted to give up his super-rich status just to work on cars?).
In fact, even in his professional life, he hates it--Remember his argument with Duck Phillips..."I sell products,
NOTadvertising." The way that was worded was important. Don has never liked making a product what it is not--he likes emphasizing what it
is. I think that ties in heavily with the theme of the show...Don always has to sell himself. He wanted someone who was honest and open--and he slowly learned Megan wasn't that. She sold herself. She presented a false image and then used it to get what she wanted.
Heck, the writers even threw in a scene of Megan turning into her new persona just for us--when she fucked over her friend for the part. That was pretty shocking, for me at least, I'd never imagined Megan as a back stabber and this is despite her friend
strugglingand having to work a full time job (Which she laments to Megan), so Megan already had a
HUGEadvantage on her and Megan still went and used Don as leverage to take the part. It was so shitty, and really showed how Megan can sell herself as something (Friend) and be something else (Back stabbing bitch.). It was how we were really smacked with her duplicity.
And that's what Don hates, I think. Because he has always been duplicitous, it's the nature of his life, it's what saved it. But I think, ultimately, he just wants to be Dick Whitman again. He's exhausted by the faces people put on.