This is really the best answer. Our office is open-plan as a rule, but there's plenty of "individually-sized" meeting rooms where you can work privately if you need to focus on something. It also serves as a good signal that you shouldn't be interrupted if you've taken one of those spots.
Obviously you need to have enough of these that there isn't competition for those rooms, but it can definitely work well.
Interesting, but I think that comfort speaks to a different issue. The office culture then is indirectly creating an environment that pressures you to act in a certain way and not acknowledging individual preference.
I agree that both is the way to go. You can find a study backing up either approach because they are important in different ways for different people.
I'm surprised no one has really brought up the introversion vs. extroversion angle. I just read Susan Cain's Quiet, and feel a wealth of clarity re: our general cultural stereotype that extroversion is better and therefore, so must be environments that are conducive to it (e.g., open floor plan. I don't have any illusions that corporations do that to save money, $ has never been a concern).
I work at a huge startup (300 people) that still has a very open floor plan and I basically work outside when it's not raining so that I can concentrate better. But the woman sitting next to me thrives in the activity and she can't work anywhere else.
I'm glad that the culture allows us to take freedom and ownership in how we channel our own productivity.
Obviously you need to have enough of these that there isn't competition for those rooms, but it can definitely work well.