In "Lady Lazarus" we see Don is growing a little bit, just as his world begins to fall apart. He gives Megan his blessing to leave SCDP (even though their conversation when she's telling him she wants to pursue acting shows that he never really understands her and isn't a good listener). He confides in his "friend" Roger, that he doesn't want her to turn into Betty or her mother, which is a startling amount of disclosure for Don, and a surprising recognition that he contributed to Betty's unhappiness. Another sign of Don's growth is that Megan turns down a client dinner in order to work (which is a lie) and he doesn't push the issue. Tom & Lorenzo noted that Megan waking Don up in order to tell him about wanting to pursue acting is reminiscent of Betty waking up Don on the couch to tell him that their marriage is over (the first time).
We don't usually get two client stories in an episode, but you don't have to look too deep to find the similarities between Chevalier and Cool Whip: they both are, or want, knock offs of the real thing. Chevalier wants a band that sounds like the Beatles, but isn't. Interesting that Ken brings in a record that kind of sounds like the Beatles, but early Beatles - not their current mid-1966 Revolver sound. Apparently cable allows you one "fuck" in an episode (which AMC cuts out), and Mad Men chose to use theirs to express how much Ginsberg dislikes the song. The conversation that the execs have about the Beatles being too expensive to get for the commercial is a bit meta because in real life, using Beatles music is notoriously expensive. It reportedly cost the show $250,000 to use the song.
Pete, you poor bastard. Tom and Lorenzo also pointed out that Pete is literally sleeping with Betty from 5 years ago, from the circumstances, to the way she dresses, to the redressing and use of the old Draper residence as Howard and Beth's house. Pete is so focused on his own feelings about the situation that he is pissed at Howard for what he is doing to Beth, but never mentions Trudy until Harry brings it up.
There are a few comedic moments in this episode: Harry and Pete at the payphone, Ken dancing to fake Beatles, and the camera panning to the awkward Cool Whip lady after Don and Megan's fight.
Additional thoughts:
Alan Sepinwall theorizes that Megan is a combination of all of Don's important women: hot and fashionable like Betty, nurturing like Anna, and good at copywriting like Peggy, but now he's going to lose one of those.
So many guest stars this season: Mr. Belding as the Cool Whip guy, Rory Gilmore as Beth, Alex Mack as Ken's wife.
The final scene is all kinds of perfect.