I've done it twice and loved it both times. The first time, there was a young man turned away. They had asked for ID's and this kid was not going to be 16 y/o until a few days later. Both parents had signed up for the tour and it was supposed to be part of his birthday gift. They kept arguing that he'd be 16 y/o in just three days and didn't think it would matter since he was so close and they'd sign a waiver for him. The CM's were not budging though and said he could not do the tour until he was 16 y/o. The parents got really mad and all three stomped out, so we had only like nine people in our group.
The second time we did it there was a couple who were probably in their early 60's and the wife was having a really hard time in training. You could tell the CM's were concerned about her, but they did let her go. When we got to the part in China where you duck to go under the tree limb, she panicked and literally dove off and let the Segway fall. The CM's were not happy with her. Then when we were over around Morocco where you weave in and out of the columns, she was exhausted and was having a hard time with her legs hurting so took a short break there while we went in and out of the columns and the CM told us about the mosaics. The main CM happened to be next to me and said that they had almost made the decision to not let her out because of the problems she was having in training and maybe they shouldn't have. The two trailing CM's spent the rest of the time encouraging her, but instead of just the one stop that you usually make in Italy, we had to take a second rest break over in the back side of the UK (by the Beatle's area), so she could get off the Segway and rest for the third time. While she was resting one of the CM's took the rest of us through the maze. As we were coming out of the back of the UK, we were so far behind schedule that we met the Segway tour that started an 1/2 hour after ours. By the time we got back to the Innoventions building she was totally exhausted and her legs were really cramping up bad.