I don't see meeting rooms as a balance. It doesn't solve the increased distraction of an open floorpan. Also, meeting rooms that are communal are not as useful- consider a whiteboard on a communal meeting room vs. one in a small office that houses 2-3 developers. That office whiteboard can have project info on it for weeks, while the communal one can't be left there.

For me, in an open office, having headphones on is not enough. There's visual distraction as well. People interacting in your field of vision are also a distraction.