I purchased a Segway i2 in 2007 and it is still rocking.
Took my daughter to school every day for about 9 years, and you cannot imagine the fun that we had with an otherwise routine activity. It is an incredible machine in my view, and electrical scooters are in a different, inferior, league as far as hardware is concerned. The Segway had the best technology available at the time, even the gyroscopes were made solely for the Segway. It has been reported to have the most efficient electrical motor at the time.
The Segway was the byproduct of the iBot, a self-balancing wheel chair. The project itself was fascinating and documented in the book “Reinventing the wheel”. After a few years prototyping the wheel chair, engineers started playing in the lab gliding the basic naked device, and looking at them Dean Kamen had a vision: to fix urban transportation in cities.
The reasons why the Segway was not a commercial success are not simple probably. It seems Dean Kamen as CEO was not very good. Was it too advanced to its time? Too expensive for mass consumption? Anyway, I believe that vision was essentially right: