They work better than closed offices, in my experience, for the roles I've worked in (software engineering).
I'm way more likely to ask a co-worker over to my desk to show them something or have a discussion if they're a few feet away within sight and earshot. In an open office I also overhear a lot of pertinent information -- I'm aware of issues that might be relevant to me as they develop, I don't have to wait hours or days for someone to communicate them in an email, issue tracker, or meeting.
There's a cost in terms of readily available heads-down concentration time to be sure, but if I want to mess around with math formulas or something I pop on the headphones, go to a quiet room, or do it at home. It's much harder to replicate the benefits of an open office environment in a closed one than the reverse.