I am planning on asking for a refund on RideMax. I ordered it before we went on our trip, and I didn't know much about how Fastpass worked or anything. When we got there, we tried to follow the schedule, but we found that sometimes we would get a Fastpass and the return time was later than what our RideMax schedule said. We didn't know what to do about this, so we ended up ignoring the RideMax schedule completely. They have a 30-day money back guarantee so I plan to ask for a refund.
I do think it would be great if you were there in high season, but we were there in January and there didn't even seem to be a need for RideMax. However, when lines can reach up to 2 hours per ride, it sounds like it would be a great tool.