The problem with open office floor plans is that every other office accommodation is also affected, but in a negative way - at least at the companies I've seen or worked in. Conference rooms are downsized as well and are given uncomfortable chairs (such as bar tools). Quiet places or "phone booths" are moved to reservation systems. Kitchens, cafes, and cafeterias are no longer respites from work, but just another area to hold meetings.
Any office implementing an open floor plan should also set aside traditional offices, cubicles, or booths that can be rented out, ad-hoc, when a serious conference call or task comes up that requires undivided attention. Moreover, these workspaces should be equipped with all of the necessary amenities (laptop dock, second monitor, etc.) so that workers can truly come and go at a whim. Having to pack up my desk and wander the halls for half an hour just so I can hear myself think over the lady having the daily conversation with her college-aged daughter or the guy slurping his coffee is not productive at all.