I think the most interesting thing about them is how fast your balance adapts to them. They're awkward at first, but after about 10 minutes on one it's almost as natural as walking.
That said, they're still kind of a gimmick. The standard model I rode wouldn't get over any but the smallest bumps, and they're too heavy to bunny-hop (I tried
. They're quite maneuverable, but as noted top speed is 12 mph.