The ones that are fourteen pages long and spell out every minute detail are irritating....probably as much because the tone seems to be that I am incompetent and incapable of using common sense to treat people like individuals.
Other than that, a lot of what people want is SOP at my place anyway, like skin-to-skin immediately after birth, delayed shots/drops, walking/position changes during labor, informing people before doing things both during labor and postpartum. No one I work with is a nipple-happy bottlemonger just waiting for you to turn your unsuspecting back so we can fill your baby full of poison AKA formula. (Yes, that was full of hyperbole, not meant to be offensive, just pointing out the defensive tone some birth plans contain. Most of us just want you feed your baby, we'll respect whichever method you choose.) Even still, when faced with a defensive sounding birth plan, I find that when people are defensive like that, it comes from a place of fear. People won't always admit that, or even realize it. It is a good opportunity to talk through stuff. Most people, even ones that can be 'difficult', can be reasoned with. Most people.
What I love, though, are the birth plans that go like this: "We are John and Jane Doe, and we are so excited about the birth of our first (second, seventh) baby. We'd like X, Y, and Z to be done, but we realize things don't always go as planned. If things need to be done differently, we'd like to know what you're doing and why, and we trust your judgment. Also, Jane wants to eat as soon as she can after delivery." (I know, I know....why do we starve women in labor anyway??)