It shows everything that was wrong and right with a past era. Each character is multifaceted and has real depth. As much as you hate Pete Campbell for his awkward selfish ambition, you also feel sorry for him because he just can't connect to people (and he wants to). Don seems to be the strong silent type but in many ways it's a facade - he isn't a war hero, he was a coward, he is a liar and he is weaker than everyone around him thinks he is. Betty Draper is self-centered and has abdicated all responsibility in her life with respect to her children but you can't completely blame her because she's been relegated to the oblivion of Better Homes and Gardens.

Of course, the atmosphere is wonderful - the show is careful to not have mistakes with anachronisms, etc. The cultural mores of the time also come through quite well.

It's slow, of course. This becomes more noticeable when you watch the show on a weekly basis, as opposed to breezing through a season on Blu-Ray (which is what I did for Seasons 1 and 2). However, even then, I still think it beats everything else out there on television right now (excepting Doctor Who, which is on effective hiatus given their silly "four movies instead of a season" idea and which I don't get here in the US anyway).