Mike,
I chuckled a bit when I read your comments about riding a bicycle. I'm 55+ and don't ride often, but I have no trouble at all, even at my age. As the saying goes, once you learn to ride a bike most people don't forget.
I have taken the Paris Segway tour (the night version). It was a lot of fun and a very unique experience. Busloads of toursists would stop and snap a few photos of our group, and pedestrians were constantly stopping us to ask about the Segways. I stopped to visit with travellers a couple of times, but the Guide was getting a bit annoyed, so I toned that down a bit.
They provide about a 30-minute training session at the beginning, and tour members are provided with a "green" or "yellow" key which limits the speed (only the Guide gets the coveted "red" key). Tour members must wear a Helmet and reflective vest, and the Guide makes sure that everyone stays together and gets across busy interestions. It's a bit expensive, but such an interesting way to see some of the famous sites of Paris, I didn't have a problem with that. One caveat however - tour members are required to provide a "deposit" (which as I recall was about €400) in case users don't follow directions and end up damaging the machine. If you return the Segway in good order, they tear up the charge slip.
The same firm offers bike tours, if you'd prefer that.
My suggestion would be to go for it!
Happy travels!