I have only really seen one segway in real life, i was riding at night in the summer around 7 or 8 and a guy comes riding along, we get to chatting. He bought his used, battery dead.
I've seen other segways for rent downtown near china town once, it lasted a year or two, maybe longer, but I dont believe I saw anyone actually riding one. They are huge!
I have seen two self balancing one wheels, but not sure if they were bought or built, one was downtown and the other deep in the hood in Marlborough while I was having a bite at BKing. They sure do look compact, and probably a better mode of transport then a segway as you could lift and carry the self balancers. The toy standup two wheel (left foot wheel, right foot wheel) 'objects' are a joke, I've seen a few of those around. Maybe for short distances, maybe there are better built ones out there. But I would go with an e-skateboard over one of the scooter types wheel ahead of you and behind you, instead of beside you.
Sur-Rons are too expensive, they look like a motorcycle so not worth it at all, not one bit if you want to ride in the city, on pathways, on sidewalks, on roadways and blend in like any other bicyclist.