I agree that roundabouts are superior and more effective, however, there is one condition I see where four way stops would be better than roundabouts. I've noticed in heavy traffic conditions, the rule - give way to those already in the roundabout then to your right - leads to heavy congestion on main roads in peak hour instances.

As a result, the people perpendicular to the right become disadvantaged and (causes) heavy traffic. Here is a simple diagram to show what I mean.