I prefer open communication than open office environment.
At my office, there are still walls and private rooms. It's a fact that there are some occasions where we need to talk private things to employees, e.g. salary, bad performance evaluation, etc.
Although my business can be considered as a startup, I don't personally think that open office environment could bring some significant benefits or any urgency whatsoever.
However, I strongly emphasize open communication to all my employees, that everyone is welcomed to share ideas (however stupid it is), argue with me, and should feel free to share any problems related to their job.