I have been there once. It was the scariest roundabout I have traversed. The contra rotating flow (inside goes one way, outside goes the other) makes it extra exciting.
On a normal roundabout if you stay in a lane (one of the inside ones at least) you'll just keep going round and round.
With the redesigned Hanger Lane you get in the lane marked for your exit and the outer lanes slowly peel off as feeders for the appropriate turnings. If you want to keep going round and round you'll need to keep moving over to the right (since we go round them clockwise) every so often to keep from being directed off eventually from your current lane.
[EDIT] It's a "Spiral Roundabout".
Not saying all US traffic circles are like that of course.
You queue for 30 minutes on the A406 with 9000 people who have left Wembley Ikea bashing your head on the steering wheel, then sling your car onto Hangar Lane like a trebuchet the moment the opposing traffic lights have gone red (not yours have gone green), slide across three to five lanes randomly, swerve to avoid the Polish truck driver who can't see you because his vehicle is LHD, avoid the police car parked on the inside to protect the previously crashed vehicle, shout "fuck you" out of the window a few times at other drivers, the traffic lights which have screwed you repetitively and any pedestrian zombies trying to short cut it across the junction and possibly several people trying to clean your windows, middle finger the BMW on your left which wasn't there two seconds ago, then desperately try to force everyone out of your way honking wildly as the 2 lanes onto the A40 narrow to one...
Followed by speed up/slow down for a bit because of the Gatsos then a celebratory victory McDonalds (and to shut the kids up) at the A312 junction a few miles down the road (or American Diner on the A40 if you want to spend the entire evening on the toilet).