My husband and I took this tour last November. Here's a description of our experience:
We showed up for the second tour of the day (at 9:15 - the first is at 8:15 I believe) at Guest Relations in Epcot, got our nametags, and were guided to the training room. Once inside, we were given helmets and had to watch a safety video. After that, we were shown to our individual Segways and spent the next 30-45 minutes learning how to maneuver on them, such as stand in place (very hard) and go through an obstacle course, go through tight spaces, etc. Once everyone stopped bumping in to each other, we headed out to the World Showcase.
The WS doesn't open until 11AM, so most of our tour was unpopulated except for the 10 of us and the 3 tour guides. We went through each country, stopping to hear interesting trivia as well as go through the obstacles in each country (such as the bridges in China and the columns in Italy).
Outside of Italy, we stopped for around 10 minutes to take pictures of Spaceship Earth from across the lagoon, use the restroom, or show off the tricks we'd just learned. We completed the rotation around the world and then rode back into the training room. By this time, the WS was open, so we ran into many people on the way back, all of whom wanted to know where they could rent the Segways.
It was a lot of fun. However, you are basically standing still for over an hour, so if you're not used to it, make sure you've stretched your calf muscles and are wearing comfortable shoes.