Yes roundabouts generally work well despite the fact that many American drivers seem to have problems with them.
There are some traffic patterns where roundabouts don't do well. I've seen the following. Imagine a four way roundabout with north, east, south and west. Predominate rush hour traffic is towards the east. Heavy traffic entering from north. More entering from west. Most exiting at east with very little going around beyond west. Entering from south can be nearly impossible since they're waiting for a break from both north and west.
There are some traffic patterns where roundabouts don't do well. I've seen the following. Imagine a four way roundabout with north, east, south and west. Predominate rush hour traffic is towards the east. Heavy traffic entering from north. More entering from west. Most exiting at east with very little going around beyond west. Entering from south can be nearly impossible since they're waiting for a break from both north and west.