The Wersi Abacus is the best arranger I've heard or used so far but I'd still love to see many more features implemented. The great part of the OAS system is the ability to continually add features and sounds without having to buy a new keyboard every few years. I've watched the Wersi grow in leaps and bounds and it's miles ahead of anything I've owned from Yamaha, Korg, Roland, and Technics. Even if the "Big Three" come out with an open system arranger Wersi is years ahead of them in R&D. It's hard to catch up when your miles behind in the race.