I've been to WDW with scooters and traditional wheelchairs -- sometimes both in one trip! Last Sept. when we were there with my Mom who uses a scooter the buses were fine. You might have to be prepared to wait and be patient. The bus drivers will assist you in getting the scooter onto the bus. My DH was there and he helped get the ECV on and off the bus most times. My Mom would ride on the scooter either up the ramp or on the lift so that she didn't have to walk up the stairs -- those big stairs are a big problem for her. After it was on, she would hop off (ok, maybe not hop...) and my DH would take over and the driver would strap it all down. When leaving the parks be prepared to wait if you leave at the end of the night with the rush. Sometimes our party would wait for 3 buses or so for the crowds to die down and then we would go on the bus. We would split our party depending on how long the line was. My Mom would wait at the front for us so that she didn't have to snake around the line and we would wait in the line. So, when using the WDW bus system, just be prepared to be paitent. Good luck!