I've tried 3 JDM drivers this summer; Kamui Works Ray, jBEAM 445 HG and a Geotech RF700. All good drivers in their own right but for my swing, the Kamui was the best. Obviously the shaft had a lot to do with it, and it wasn't perfect as the sound was too muted for me, but the feel off the face and the ball flight were spectacular.
I'll buy one.....eventually, but will have to try a Yamaha before I make that purchase!