The Open University is migrating from Moodle 1.9 to Moodle 2.0/2.1 to take advantage of new features and enhance custom modules. With over 770,000 users accessing over 500 courses daily, performing the migration while the university is active poses challenges. The migration will be done progressively as courses end over multiple years to minimize disruption. Performance has been tested and infrastructure expanded to support the higher volume. New themes and mobile optimization and annotation tools will enhance the user experience in the new platform.