They are also much nicer than stop signs because you don’t have the issue of people waiting to let others go, not knowing who goes next, etc. Just make a right onto the roundabout when you have room. Make another right when you get to your street.
And when they are empty, you barely have to slow down at all (if you’re being obnoxious, you don’t slow down and just chuck the car through it at 35mph.
On another note, I’d wager that roundabouts are better for fuel efficiency as well, since most of the time you don’t come to a complete stop and have to accelerate back up to speed, but instead just slow down until you have an opening. If I remember correctly, fuel economy was a big part of the reason for the 55mph speed limits.