Roundabouts are a bit like traffic lights but which never keep you waiting on red when the other routes are clear. I have seen them installed and make a huge difference at junctions which were previously really dangerous. Consider trying to cross the main road shown below.
The roundabouts force people to slow down, reducing the risk of accidents and also the severity of any collisions which do occur. They are also fairer as everyone has a better chance of making progress.
I am a big fan of maintaining progress at roundabouts, of course, only when it is safe to do so. Good observation before entering the roundabout, both ahead and behind often allows you to enter the roundabout at a faster speed and "straighten-it-out" allowing a more comfortable passage through. However, remember to consider use of your indicator to help other road users know where you are going.
The use of roundabouts however can also be abused. I have seen many people jumping a queue of traffic waiting to go across a roundabout by using the clearer right hand lane. They then go all around the roundabout before exiting straight on. Whilst not technically illegal, it is inconsiderate not only because of the queue-jumping but also because it greatly reduces the roundabout’s capacity. The queue-jumper is taking a path not intended by the roundabout designers and impedes the progress of many other road users taking other routes through the roundabout.
