It is powered by six medium PF motors with six linear actuators and three IR receivers. It is controlled by a single NXT with the HiTechnic IRLink. My version doesn’t have any feedback, so the motors linear actuators are turned on and off based on time. It took a few hours of research to get the linkages and joints down, but once I did that, building and programming took only one night.
Movement is sloppy because of the PF motors. I want to try to build this using servo motors, but mounting the huge motors is a problem.
Here is what a well built Stewart Platform should look like...