I think part of the satisfaction of this season so far is that we've always known that Don Draper is a bad guy, but we're finally seeing that realized. You get so swept up in his charm (and Jon Hamm plays it pitch perfect) that if you're not actively reminding yourself what horrible person he really is. The kicker is that we want to forgive Don, so it's easy for us to do so when he really does something shitty. This season we're being exposed to his downfall and we're getting, for the first time really, a chance to see him at his most flawed. Of course, this will mostly make us root for him to get it together, but it should be a great ride down.
For some reason I really feel like Breaking Bad being so good, so unpredictable, with a protagonist who is making such bad, bad, bad, bad decisions has affected the writing staff of Mad Men. I feel like Don and Walter suddenly have way more alike than they started with. Including the Shakespearean tragedy they are befalling on themselves.