There's another even crazier one in Hemel Hempstead. This one has 6 mini roundabouts in it and two lanes: the inner lane lets you go counter-clockwise, the outer lane lets you go clockwise, and the mini roundabouts let you switch. Oh, and there's a river running through the center that isn't visible from the road, so if you try to cut through, you get stuck. This quote sums it up: "When it opened in June 1973 a police officer had to be stationed at each of the mini roundabouts to prevent chaos."
For another example of crazy road design, closer to home, check out Kelley Square in Worcester, MA. It might look tame at first glance, but notice the sheer number of roads feeding into it, the utter lack of traffic lights, and the archipelago of islands in the midst of a long bed of asphalt. I especially like the bit at the top, with five roads feeding into a great open asphalted area. Great for playing multiple games of chicken.
Of somewhat lesser horror (but definite anxiety to newcomers) is the cause of much traffic build-up near where I work: Oak Street Intersection, Natick, MA. It's a sad attempt at a roundabout dropped right on top of a four-lane highway. There's some classic behavior at rush hour where those little outer parts of the arcs fill up to about 4 cars each and the whole thing jams, because of course it's nearly a deadlock situation when you can only fit 4 cars into the only lane for going in any direction but straight.
* It should be noted that in the 25 years that the Magic Roundabout has existed, there have been less than 15 major accidents and less than 60 minor accidents. Though I think that's less a testimony to a good design and more a testimony to the ingenious adaptive abilities of the Swindon residents.