The CP40 has an excellent keybed which in my opinion is superior to the more expensive CP4. The action is heavier and feels much more like a real piano. It includes high quality sounds and is relatively easy to use (if you read the manual). The weight has been kept low because of the plastic casing which is acceptable if you protect the piano with a case or a padded bag for transport. The external power supply is unfortunate, but Yamaha have to somehow justify the increased price of the CP4 (which doesn't have one). I use the CP40 as a controller and so far it has performed very well.