Having just written about a scientific conclusion that boarding passengers randomly would be more efficient than the back-to-front method of yore, I had a chance to experience it. Six times.
I flew on a Northwest 757 from Bradley to Amsterdam and, after boarding business class and elite fliers, the gate agent simply announced that all other passengers could board. The same thing happened on the return flight, and on my KLM flights between Amsterdam and Istanbul.
And when I flew between Istanbul and Kayseri, Turkey, it was the same deal – minus any early boarding – for flights on an Onur Air MD-80.
All in all, I think it worked fine. Instead of having people clumped in one part of the plane, all trying to stuff their bags into the same overhead bin, the action was more dispersed.
Perhaps the age of boarding by rows or "zones" is over.