Back in the 90's the local skateshop tried selling the first generation ones. They bought the hop up kit and since I was the only guy who knew anything about motors, gave it to me to install it.
Thing did like 45mph with the little hard rubber tires. I beat the shit out of it, wore the tires almost to the rims, and when they asked for it back, I got pulled over and the cops impounded it on the way to the shop.
There's guys that race them on kart tracks. They were racing with us at our motorized bicycles races, and I had to make sure I was stocked up on ear plugs. You think mopeds with no silencers are loud, wait till you get around 40 gopeds constantly revving their little motors.