I was the engineering manager at my previous employer and we were reconfiguring our office layout. I talked to the engineers and with one exception each person wanted private offices. We set up one floor of the office with high cubicle walls, and a lot of sound isolation. So not exactly private offices, but really a pretty nice setup (with the best equipment and furniture available).

On a separate floor we had a bullpen with ops folks, people who were on the phone a lot, etc. One by one, each engineer gravitated towards the bullpen until no one spent more than perhaps 1 day per week in the dedicated office space. The part of the office that each engineer had claimed to want to work in became abandoned.

I think, in spite of the theoretical want for quiet space and isolation, there's a very human need at work to be in the middle of the action -- to hear what's going on, and to be connected to your colleagues. There were certain tasks and problems for which engineers would walk downstairs and make use of the dedicated space, but it was ultimately not where folks wanted to be on a daily basis.