I'm still going to opt for (at least semi-)open workspaces though. Despite the downsides, they encourage communication a lot and it also feels more relaxed. I think most of us know how often a lack of communication is the cause of trouble.
Putting teams (either functional or cross-functional project-based) of 3-6 people each in an open workspace is great for communication. On the other hand, putting a whole office floor as a single open workspace will simply kill productivity and discourage communication because either people will be isolated in headphones so they don't hear their neighbor, or people will avoid discussions there ('let's get a meeting room') so as not to disturb others.