I'm not keen on them because I've seen them in use around here. They're wide; especially if you have the little hardcase panniers for them. They take up much more than half the sidewalk, forcing people out of your way. They top out at ~12mph; far faster than anyone is walking around. I rarely see the Segway riders keeping a slow and steady pace with any other pedestrian traffic. They're weaving around people like a kid on a skateboard. Finally, they're squirrelly for new operators; much like a bicycle. Except that Segways are allowed, if not specifically confined to the sidewalk with other pedestrian traffic.

Conceptually, I have no complaints. In practice, I'm just not diggin' them.