Forfar got it's first roundabouts in about 2001 (just the wee painted fuckers). It's astonishing the number of locals who still don't know how to deal with them. I've lost count of the number of pensioners who I've seen just straight over them without checking the traffic from their right. Between those and ridiculous Mexican standoffs where three drivers all sit looking at each other wondering who's supposed to make the first move. Hopeless stuff.
The example which comes to mind, to illustrate my point above, is the Bankfield roundabout on the A77 at Ayr. For a start, it isn't round, more of a parallelogram. As you enter on the 77, both from north and south, there is a long straight stretch into the exits. It's here where a right signal is useful to the waiting traffic trying to enter the roundabout. They are uncertain whether traffic on the roundabout are exiting as you can't rely on them indicating left.