Yes, my brother and I did this Summer 2004 and it was great. There are many on the
DVC board who have done this and have posted on other threads in the past.
Basically you're correct, one hour of training and one hour through World Showcase. The training involves basic Segway controls, moving, stopping, turning, going up/down small ramps.
The Showcase tour is basically follow the leader (tour guide) through many of the large and small paths found around the different 'Lands'. Some of them are a little tricky and the training really pays off.
You stop for awhile for a photo-op session, and 'free' time where you may just ride the Segway around in an open area, just for the fun of it. On the way back, when you get into the areas of Epcot that are open, it's fun to listen to the comments of guests who see you go by. Probably the most common one we heard was that we were CM 'trainees' of some kind. Very few people really know it's a tour.
If you're interested, definitely go for it. Riding the Segway is easy once you get the basic hang of it. When we finished, they gave us a special Disney Pin, basically Epcot with a little Segway that actually slides left and right on the pin.
This is how it was for us 18 months ago. I'm sure if it's different now someone else will post. We'll be doing it again sometime on a future trip. Maybe this time I'll get DW to try it......