A quick review of 2 YES classes taken by my DS6.
1) How Things Move at MK. DS loved it. Good activities to get kids thinking about how things move. Our leader was Megan and she was great. We rode on Pooh, the Carousel, IASW, and the people mover (no front of the line access so be prepared to wait in line).
2) Synergy in Science at EP. DS liked this, but I wasn't all that impressed. I think my lack of enthusiasm has more to do with the leader than the class. I won't say her name, but she was very...ditsy. She had a hard time making decisions, she didn't have a loud voice, and she was not very authoritative. She frequently forgot the words she was trying to use to get a point across to the students and then the whole conversation was lost on the kids. We rode on Spaceship Earth, Captain EO, and Figment. I heard other leaders being very enthusiastic, encouraging, and making sure all the kids got to participate (we had a couple of very dominant children in our group who blurted out all the answers and got most of the time with the hands-on demonstrations because our instructor didn't promote "sharing"), so I think this program could be very good with the right instructor.
Overall, we had a positive experience and would definitely sign DS up for other YES classes in the future. It helped us justify pulling him out of school, we got discounted tickets, and DS had a lot of fun.