I never cared enough to save them, but have come across several articles claiming that open workspaces do indeed cut productivity. As some here have alluded, productivity does not necessarily equate to quality, or for that matter, creativity. And there are other company culture issues to take into account.
Having worked in a number of different environments, I've never heard a complaint that a space was too closed, and have heard many complaints about open workspaces. And in cases where there were a mix of open areas or cubicles and offices (solo or shared), I don't know of anyone who said no to moving into an office. I'm sure the complaints and preferences are not solely related to productivity, though.