I can't think of a more startling transformation of a character on this show (other than maybe Peggy) over the course of seven seasons. Harry's descent into being the worst human being seemingly contradicts the show's hypothesis of "no one ever changes, nothing ever happens". Let's review his devolution and imagine what the show would be like without him.
Season 1: Harry's one of ad boys at Sterling Cooper, but the only one who hasn't gone to an ivy league school. He seems more down to earth and has an honest relationship with his wife, Jennifer. His flirtation with Hildy results in a drunken one night stand which he immediately confesses to Jennifer. Harry seems actively remorseful and contrite, spending nights in his office after being kicked out of their home. During Don's infamous Carousel pitch, Harry tears up and leaves the room crying.
Season 2: After reconciling with Jennifer, Harry confides in her about problems at work, and takes her advice about getting a raise.He spends the rest of the season floating along, being mediocre as all hell. Joan helps with out with work, and he promptly forgets to credit her in any way, shape, or form. A familiar tale. Kudos to him for trying to find a sponsor for a TV show about abortion though, which gets Roger's attention and earns him his first of (mostly) undeserved raises and promotions. If he hadn't been around, Joan might have gotten the media job. She also had a knack for recognizing branding potential.
Season 3: This is when things take a FUCKING turn. Harry's inability to deal with a drunk Lee Garner, Jr and his lack of initiative to inform a senior partner about Lee's demands get Sal fired. SAL. Beautiful, lovely Sal. Unfortunately, because Harry is the only media person they have, he is invited to join the newly formed Sterling Cooper Draper Pryce.
Season 4: Harry is mostly seen in drips and drabs, procuring Beatles tickets for Don, flirting with models in casting calls, hitting on any woman within eyesight, letting his sideburns grow long, jetting off to California, generally abusing his position of privilege and power.
Season 5: Despite how inappropriate you thought Megan's "Zou Bisou Bisou" dance was, you keep your mouth shut about it at work, Harry! Although without Harry's lewd and unnecessary comments, Megan wouldn't have left work early to "clean" the apartment in her underwear leading to one of the hotter Draper sex scenes. Harry takes partial credit for the Heinz pitch, despite not contributing at all. He sleeps with Kinsey's girlfriend, when Kinsey clearly needs his help and support. He does give Kinsey $500, probably out of guilt.
Season 6: Harry Crane is a lost soul, once a victim of and now a perpetrator of various systems of oppression. He petulantly demands a partnership by calling out Joan, and seems to spend most of his time "networking" aka boozing in LA.
Season 7: Once again, Harry gets someone outed from the agency this time with the aid of a large computer. This time his poor victim is Ginsberg, whose paranoia and mental health issues are triggered by the presence of the monolith and who eventually cuts of his nipple. Harry continues to demean Joan's authority, and is petulant about wanting his partnership. He eventually gets it, but with the new McCann Erikson merger, his status is unclear.
This all culminates in one of the most squeamish and hard to watch Harry Crane scenes in this week's episode. He blatantly hits on Megan, and it takes him all of 2 minutes to propose sex in exchange for a favor. When rebuffed, he runs to Don to cover his ass. Harry Crane isn't evil, even though he's probably the closest this show has to a villain. Even spoiled, imminently dislikable Pete is treated as a source of comedy (poor Vincent Kartheiser's hairline). As much as Pete represents the old guard, the entitled white man born into wealth and social clout, he has also shown flashes of progression. His is a latent racism and misogyny, the kind that still exists today. Harry Crane, on the other hand, doesn't get the Pete treatment. We've witnessed Harry get promoted just for being at the right place and the right time, for mediocrity. Once within the agency's upper management, Harry has abused his position and is clearly desperate for validation (he still worships Don and tips him off about Don's possible firing).
The other characters on this show at their core still resemble their Season 1 selves (other than Ken going over to the dark side as we saw last week). Harry is now firmly ensconced as the lowest of the low, his devolution from hapless ad man to perpetrator of awful traditions. In that way, Harry is a fairly fascinating character. His background is not explained like Don's or Pete's is. He is entirely a product of this age and environment. Harry is also the character we are likely to see in real life today. The kind of person who, once given one step up in life, believes they are deserving or entitled to the next one. He can't fathom why Joan made the choices she made regarding Jaguar. Maybe if he had hired her in the first place as a reader, she would have had the opportunity to work her away up. As much as I'd like to imagine a Harry-free Mad Men, he is pretty integral to the show. Don might be resistant to change, but Harry has clearly been shaped by power, greed, ambition, and privilege.
I guess other things happened this episode too, but frankly I'm tired of Don's dalliances with troubled brunettes. Another one of Don's old flames was trotted out for one more trip down memory lane. Does this mean we'll see Midge or Suzanne next week? Poor Midge. We also got a Betty and Bobby 3 appearance (!), but no Sally (boo). Also, where is Cutler? I know he wasn't guaranteed a job in the new agency but I miss that silver fox.