Our office has about 60 people in it across 2 floors and everyone uses a shared open space, and I really do mean everyone. Our founders and ceo are right out in the middle of the open floor along with everyone else. We have plenty of space for people to conduct meetings or shut themselves away with their laptop and phone to do personal work. There are plenty of couches you can sit on to get your back to the wall if you want to take a break and have some privacy.
The amount of ideas that flow around our office on a daily basis is amazing, and if nothing else I hope they work to preserve this arrangement. Sure there are people who don't like it, and you know what, when they leave we're BETTER for it. This company more then any other has taught me that it's important to foster a workplace culture even if it means leaving people behind.