At most organizations I've worked at that use an open floor plan for programmers, we pair-programmed aggressively. Subjectively, a good pair more than offsets the distractive drawbacks of an open floor plan. If instead you hand each programmer a pair of headphones as they walk in the door then yes, productivity's going to take a hit compared to closed offices. Working in isolation in an open floor plan is worse than working in isolation in offices.
Pairing is an inescapable all-day distraction, so I would expect it to trump other distractions. If I were to accept never ever getting into the Zone at work, I wouldn't be frustrated and less productive at being pushed out of it. But I'd rather flip burgers than spend my entire career talking instead of pondering.
