To me the problem that they didn't address, though, is rush hour. I've seen the problem both in the US and the UK where when a lot of traffic is moving from one side to another point, every other entry downstream of the main flow becomes backed up because there's no opportunity to enter the roundabout. I'll try to illustrate using this diagram I found:
Imagine it's rush hour, and most of the traffic is moving from the left road to the top road. It's pretty much a continuous stream of traffic, and those drivers in that stream are relatively happy because they're moving through without having to stop. But the drivers trying to enter the traffic circle from the bottom or the right roads have almost no chance of getting in because the traffic from the left is not being stopped. Their only hope is for someone to enter from the top road, pass the left road, and get off at the bottom or the right. If they get off at the right, it still doesn't really help the bottom road. Alternatively, if someone coming from the left isn't actually going with the rest of the flow and gets off at the bottom or the right, it can let someone in from the road where they get off. Of course, both of these tend to rely on people signalling correctly for the intersection (essentially the signalling works the same as a traditional intersection; if you're coming from the right and exiting out the bottom, you should have your left turn signal on until you reach the street you're exiting on, at which point you would signal with your right turn signal), which I don't recall ever seeing happen in the U.S. The overall throughput may be higher as the Mythbusters found, but for traffic that's not part of the main flow the throughput becomes much lower than at an intersection that stops traffic and allows cross-traffic through.
Another problem with at rush hour is if somewhere further down the road with the main traffic there is an intersection involving a stop then traffic often backs up into the roundabout and blocks everyone from getting through the roundabout.