I tend to shy away from making vast statements that involve the word "everyone," because there are always many exceptions to those rules. But in this case, I think I can safely say: everyone who fancies themselves a writer should be watching Mad Men.
And I don't mean "watching Mad Men" in the sense of having it on in the background while you eat dinner or check your Facebook or chit-chat about your day to your roommate. I mean WATCH watch it -- turn off the lights, light a candle, pour a glass of wine, and focus on that television the whole time, taking note of all the intricacies of the language and dialogue.
There are very few shows which require me to do that. (And in fact as I wrote out that sentence I was desperately trying to think of another show for which I do that, and I failed. Oh wait! Now I have some, though they're oldies. The X Files. Sports Night. Veronica Mars.) One day a while ago, I talked about how watching General Hospital makes me a better writer. And it does, but in a much different way than Mad Men does.
I languish in Mad Men. I take my time with it. Kind of like how I re-read my favorite Edith Whartons each year, slowly and with great care, just enjoying the words -- that's how I am with Mad Men. I let it take up all the space in the room for the hour. I let it entertain me. Every word of dialogue is used to within an inch of its life. It is all necessary. It is what makes the show so smart, so subtle. And while I adore the styling and the politics and the actors, oh my goodness the actors, I stay for the writing.