But where they would not work for me is the ability to feel the ground all the time, from texture and incline to cracks and random objects. I wear regular trainers or skate shoes most of the time, but even in heavy boots/sandals designed not to have any flex in the sole, tactile feedback is important. I just can't see the wheels and gears delivering that the same way, nor lasting through the varieties of surfaces and forces that hard walking involves. I feel they would work great in a campus environment where you can high construction standards.
A less obvious issue is that fast walking isn't just a fitness/surface matter. Most people are slow so maintaining a steady pace requires a surprising amount of lateral movement and mini-pivots, shifting one's weight around and so on. I suspect the blissful gliding depicted in the product videos involved a level of mutual awareness of and respect for other people's space and momentum that is often lacking in busy environments.