Yeah but - does it go over water too? That'd be something cool you can't do on a Segway. I don't know what kind of power these things have, but it could be a cool way to tow riders back to the top of the hill.
I bet you could go pretty fast going down hill. If you're hovering over the road surface, and the surface is slanted, you're essentially friction free. Seems like you'd be zooming down the road in a heartbeat. All you'd have to deal with is the wind resistance. You'd look pretty funny trying to footbrake though.