Better than any digital piano I've ever played. As good as my Yamaha YUS-5 upright, and in some ways better. Played alongside the Nord Piano 2 HA88, RD700NX, MP10 and the MP11 is in a different class. Gives control and responsiveness like I've only really felt in a (well conditioned) £15K+ grand piano.
Sounds are ... fine. Bought this over the VPC1 because I will occasionally gig with it. For gigging, the sounds will stand up just fine, and cut through the mix; it's a stage piano, and it feels like that's what they've been designed for. Playing lots of solo piano at home, well to do this justice you'd want to hook it up to a good software piano library.
As a midi controller
I've been using Eastwest Pianos platinum, but also have Ivory 2 and NI The gentleman. In all cases the velocity curves needed only a tiny bit of fiddling (in the software) to be just about perfect. Hooked up to EW platinum it really feels incredibly close to playing a 50K piano.
This isn't a stage piano. If you're gigging all the time, get a Nord - the sounds are way better. It _is_ the world's best piano midi controller that you *can also use to gig* (if you have a forklift truck), because it has a few fairly decent onboard sounds. As a master controller with added gigging ability, it's the best thing I've ever seen.