I became used to them while living in New England, but I did not like them. In the more populated areas they just seemed a worse way for the maniacs to drive like idiots.

We have one which works well, here. They are getting ready to put in a few more. I don't think they are a good idea. If you can imagine, the worst one we have is a gigantic thing stretching from one exit ramp to the other on I70, four lanes of traffic, two lanes each for each exit ramp, all of them converging on a super-duper, super-confusing roundabout/traffic circle above all of that traffic whizzing by below on the highway. Most of the folks getting on or off are not familiar with the area and are going over 70 when they hit the exit ramps. We've already had one semi turn over. It is crazy and we avoid it like the plague.