The problem I've had with things like this is that I live in a northern climate - these won't do winter well. Second, where I live, it's still a fight to get decent bicycle paths put in so one can ride safely. These things would absolutely have to have their own lanes. Cars are already crowded and drivers distracted without adding this to the mix.
In other words, we'd need some social changes to take place before we could see wide use. It's possible, but just manufacturing and selling them won't bring about the needed changes.
Still, I bet they would be fun to cruise around on.