As a summer student in 1999 I saw the Segway's gyroscopic technology evaluated in a stand-up wheelchair form by https://www.herl.pitt.edu/. This research lab sat between the University of Pittsburgh, Carnegie Mellon University, and the Veterans Affairs department. The lab still exists.
The wheelchair hit the public as https://en.wikipedia.org/wiki/IBOT. I knew it as "FRED". I have never observed anyone using its equal in terms of mobility capabilities.
My skepticism was rather about Segway, the product, being useful as a mobility device, and recognised as such by European regulators.