roundabouts...errr, they call them "traffic circles" around here and they are slowly disappearing
Circles were quite common until a few years ago in the outskirts of Philadelphia, specifically on the New Jersey side of the river where most "major" intersections used to be traffic circles. Now many of them are gone, converted to more conventional intersections with stop lights, etc., and the few remaining ones are doomed to a similar fate in the near future.
I actually enjoy it when I come across one. Especially with my kids in the car, since I've been known to just start looping around the circle a couple times until the kids excitedly say "dad, why are we going in circles!" and then I'll cut off to my intended direction while explaining my traffic lesson to them. To put my antics into perspective, the kids also get "overly excited" when we're just cruising down the highway and I suddenly start blowing my horn...of course I only do this when no other cars are around, but I find it funny how some people in the car freak out for no reason just because I'm blowing the horn a few times. As if there was some universal law against blowing your horn even if nobody is around to hear it...except the trees in the forest, of course, they hear it.
I never really had a problem with traffic circles, though I can see that there's not enough space for them in many urban areas. Circles make sense to me since you don't have to stop if there is no reason to, just slow down and carefully merge with the flow. It is self-regulating but dependent on common sense. And for those not familiar enough with how to drive around a circle, I suggest simply adding the topic to driver's education programs...you stop at red lights, you merge around circles, etc.