Saw a young guy at Heathrow last night on one, cruising up to the car park ticket machine.
However as they are much wider than the single wheeled units I think they are less socially acceptable – meeting a single-wheel rider on the pavement isn’t a lot different from meeting a walker as they are no wider, but meeting someone on one of these is different.
And from reports I have seen people do seem to be quite accepting of riders on the single wheeled versions. I can’t see the same reaction if they have to step aside to let it past.
And another issue is obstacles – their wheels are much smaller so obstacles will be more of a problem, and I have seen people complain with the double wheeled unicycle versions that obstacles tend to cause the unit to try and turn itself, which is a PITA.
If I was to get a device like this I would be looking at the ninebot ones.