Don recognizes a fellow talented "misfit" in Peggy !

to me, it was a confirmation of the fact that business is more real to don than his personal life.

I think don't think despite his campaign to get Betty back at the end of Season 2, that Don had really begun to fight for the women in his life until this season.
Let's look at it this way.
He never had to fight to make Peggy a copywriter, etc. because he was in charge. He did fight to bring her back from the dead emotionally with his advice to her in the hospital, but at that point, she was not that important to him other than as a way to punish Pete.

He did not fight at all for Midge-he must have not cared that much or realized it was time to move on.

He did not fight at all for Rachel. He could have gone back to her after he and Pete left Cooper's office and his job and identity were safe, but he just let it go.
Now in season 3, he really tried all season to make things right with Betty and only began his affair with Miss Farrell after the return from Rome and the realization, at least on some level, that he was never going to really get Betty back. I don't count the one nighter will Shelly the stewardess as an affair or even anything of meaning to Don.

If we wondered why at the end of the finale that he called Betty and told her that he wasn't going to fight her, that's the answer. He had been fighting her (or for her) all season long, and with the fight he had just been through for his professional life, he could not fight anymore.
He did fight for Peggy in the finale. He realized that she and he were a lot alike, and if he could bring an uneducated farm boy like Dick Whitman to the pinnacle of the Advertising profession, that Peggy could do the same, and that was too valuable to just let go.
Unlike some have speculated or even advocated, they are not going to end up as lovers; it is going to be even better between them, Don is going to have his first real friend. Peggy too, perhaps.
I am so excited about season 4. I hope it is a season of realistic growth, not just change. A lot happens historically in the US in 1964, and I am eager to see how our favorite characters handle it.

It seems as though Don’s most successful relationships are with those women he holds in regard for their moral and intellectual capacities. Betty, while complex in her own way, is selfish and reserved, and after awhile beauty cannot negate the sufferings of a bitter woman. I’d really like to understand more about Don’s relationship with the woman who raised him. I think the relationship he had with her must have been a loving one, or he would have no regard for women at all, because his father was jerk.

I don't think it was loving at all. The exchange Don has with Adam in 5G, Season 1, when he meets him in the diner and asks about "her" kind of lets us know that their relationship was not good at all.
I think it is a miracle he's not more messed up than he is after being called a "whore-child" while growing up. He alludes to this also in Season 1, The Hobo Code.

I think Don and Peggy have a special bond and trust and respect each other, despite their personal
history.. and Betty saying I don't love you, was devastating to Don..

I didn't get to see season 1.(thanks for the update) I've been wondering about that for sometime, because he does seem capable of loving people. Given the glimpses we've seen of his childhood I thought he must somehow at least have seen an example of what loving relationship is, to at least strive for it. He clearly loves his children and has genuine affection toward them. That is something that typically doesn't come naturally if you have not experienced it in your own childhood. I wondered if he called the "mother-figure" - "her" because that may have been what the Dad called her...(and since he asked about "her" makes me think he must care somewhat, yes?)

2 words: Sex Addict
May I have a 1963 Mad Men calendar, please?

The question should read, Don's fight for his life. The final meeting with Hilton, and the allusion to Hilton's reference to him as a cry-baby, was, in my opinion, a turning point for Don. That's Don's epiphany and from there, he makes the decision to take control of his life, its direction, and the legacy he wishes to leave behind.
From that point on, he seems to be investing in people who will pay off. And people who would be onboard with his new attitude/journey. Betty is a lost cause. He can never make her understand that, in his mind, he had no choice (about his identity-switch) and that his pride prevented him from being able to reveal the truth to her or anyone. She remains on a pedestal to him, and I believe his infidelity is partially a result of his own denial of his reality. Translated, how could a woman like Betty be with a man like him?
Hilton ultimately gives him the confidence to make a name for Draper, even if it isn't his own. Don has a new clarity and when the fog clears for Betty, she'll come running back.

Betty is so delicious to look at and in season one when she said that she wanted Don "So Badly" it was enough to make any man melt. But...not Don, he rolled over and turned off the light. He has been in control of that relationship since day one and remains so...because he will not grovel like this parthetic Harry has and will....she will tire of him for this very reason. Betty want's Don back and will come crawling, because he will not be owned.

Why do you think it killed him to sign the contract with Sterling Cooper? He want's his autonomy and has to have freedom...that's what Midge was for him...an escape, freedom. Rachel was a chance to make a break for it...total Borderline Personality! It wasn't Rachel....after all she wasn't that close to him...she was only an escape!

Peggy is brilliant just like Don, they are exceptional people, while Betty is striving valiantly to be like everyone else! Of course Don is weary of her....she is only exceptional in relation to him!

As for character Betty portrays..It is how she was brought up....yet she seems to want more as most women did back then...Don cheated and left out a HUGE mystery of his past to his wife. He seems to be a lost soul. As for Peggy..She is one of not many in that time period. God bless the women that lived in that era!!!, Glad I did not..........

Business is easy. Well, easier. Relationships are hard.

Although he like likes her personally he recognizes her talent. And he recognizes there is some of her in him and vice versa.

Botton line for Don: business is business, personal is personal. How else can one keep track of all those lies?