While I do agree, I've gotten quite a lot of work done in open floor plan offices. Enough that I think it's fine to start with, especially since our company is so early stage.
I worked in an open floor plan office for 8 years. The second best results invariably came from projects in which my 3-4 man team claimed a meeting room and closed the door. The best results came from working from home, where I have a private office.