Sure, the Segway has advantages too - but when people suggest that it should go at 25mph in city streets, it's worth considering whether the Segway's unique properties actually contribute anything. Different tools are better for different jobs.
I'm all in favor of thinking outside the box, but things like cargo bicycles are more practical and interesting (though less sexy and high-tech) for my own city transportation needs: http://www.xtracycle.com/cargo-utility-bicycles.html
A closer comparison is a scooter or moped type of device. Those will fit through some doorways, but being gas-powered they are generally excluded from use or storage in most indoor areas. Cost is comparable, although the scooter would win out on distance and top speed. Most scooters are also too heavy for a single operator to pick up and move, and they also don't generally break down to fit easily in the trunk of a vehicle.
Segway's, even the non off-road models do quite well on dirt/trails, so that isn't an advantage for the bike. They could go in the streets as well, the only limitation there is erratic legislation, so it's hard to make a direct comparison.
The general public bias against Segways is kind of understandable. Most people aren't capable of thinking outside the box. I'm always a little surprised when the hacker/entrepreneur community seems to jump on that bandwagon though. Even moreso today when so many people claim to be "green" advocates and will proclaim that we need to explore other modes of transportation, yet bash anything that doesn't have 4 tires and a steering wheel.