A few things:
1) Having my own office did not mean that there weren't distractions. It's impractical to build sound-proof walls between offices and the guy across from me loved to try to sing opera for hours a day. I eventually moved offices to another part of campus for that reason.
2) Likewise, I've worked in open offices that were pretty monastic. Engineers are quiet, everyone is wired in and most people talk on Slack/HipChat. The only interruption was when the mailman would drop off the daily mail.
3) I think the worst thing about open offices are the logistics of staff that need to take phone calls. As a customer-facing programmer that does sales support and configuration assistance it's sub-optimal not having a dedicated space for phone calls. When the perfect storm arises of too many people needing to take calls, everything flies into anarchy where I'm forced to take a call in a common space and try to be quiet. A bullpen that has some separation and accommodation for those needs is ok. A bullpen that doesn't have that is not.
[1] http://www.xconomy.com/wisconsin/2014/09/19/epic-hopes-wi-ca...