Then there is this cluster fuck of a roundabout in my city Lansing, MI. Yes they do have a full STOP sign at each entrance to the roundabout for the crosswalk not just a stop for pedestrians which would make more sense. So you have to stop then yield to circle traffic then go. The entire roundabout is useless because once you stop you lose the benefit.
Roundabouts are not just for efficiency, they are for safety. A regular 4-way intersection introduces multiple conflicts between cars turning left and cars coming from the opposite direction.
A roundabout only has one conflict for each connecting street, and the right of way is clearly defined.