It's the angst I can't stand, really. Makes me want to shake people. And the repetitiveness; the whole male-lead-female-lead will-they-won't-they has been done to death. As a character arc, okay, but people actually do make decisions about these things, and change over time, and when the same two characters are in the same maybe-we-will-maybe-we-won't-let's-tease-t
Buffy does fairly well here, actually; there's angst, but there is also change, and nobody pines after anybody for the entire series. Wash and Zoe on Firefly are an excellent example of a good, fun, established relationship, although both Simon and Kaylee and Mal and Inara make me want to throw shoes at people. (Eh, it only got a season, maybe they'd have fixed it.)
Leverage and Castle are both seriously starting to grate. We are about to get the next season of Leverage from NetFlix, and I am getting kind of trepidacious. I was really enjoying the subtle background bits with Parker flirting with Hardison and Eliot, and then towards the end of season 2 Hardison noticed and starting... angsting. Nate and Sophie are already obnoxious enough, I do not need more romantic tension in this show. Especially with Parker, sheesh. At least it won't be the both of them doing it, even if the writers do insist on going there with Hardison.