My late 50's neighbour recently bought one, but the style where you face forward with both feet on the side. It looked like there was a bit of a learning curve, but he's got the hang of it now and seems to really enjoy it.
I think I'd be more tempted by an electric longboard, though the OneWheel's look super cool. And I'd guess the larger wheel would make fior a smoother ride than a longboard.
Since I can't bike due to a knee injury, I've been thinking of getting one of these for quick trips to the grocery store/errands. Would save me from having to get in the car. But, I just can't bring myself to pull the trigger.