Very Good. Not Perfect.
I am very happy with this digital keyboard, but wanted to mention where I feel it could be improved. First of all, I play keyboard in my own trio (jazz, fusion, funk, blues, etc) and have two KC-550 amps for stereo sound. The 128 note polyphony is good, but when you use 2 patches combined, things change. Notes DO drop off, first of all, especially if you like to play with some sustain to make up for the short duration of the actual patch's sustain. If you listen to a single note, the sound is excellent for about 3 seconds, then it loses most of its beauty and it becomes obvious that you are listening to a "patch" rather than a true string vibrating in a wooden piano body. To overcome this, I use slow strings under my keys, much like what Brian Auger is doing these days. It fattens the sound and fills in. If you play staccato or don't hold your chords down too long, you won't notice this, but I play with drums and bass, as well as sing, so the piano is the "orchestra" and I would like to have true sustain and natural decay. This is a fault, in my opinion. I'm looking at the new, very expensive, Yamaha grand and the new Roland V-Piano as a possible replacement because of this reason. As far as the keyboard "feel," it is also very good, but not as good as I would like. I play hard and, while it's better than anything else I have played, I still beat the crap out of my hands on 4-hour gigs. It seems to me they could engineer some kind of pressure-reducing strip, like what you might stand on if you have to work on concrete floors all day long, to prevent the hard "bottoming-out" that I get. It would work normally for those who don't play quite so hard, but save me from stress-fracturing my fingers when I'm pounding it.
One other thing...if you don't like the original sounds as much as you thought you might, you can make HUGE improvements by going through all the parameters of the individual voicings to improve them. I've done changes to most all of the patches I use and they are FAR better than the factory pre-sets. Just be careful not to overdo it, and keep the original settings somewhere, so you can fix things if you get crazy. And by all means, make sure you are using two amps. Stereo sound is a WORLD apart from a single amp. I use Monster cables and they are good. There's a new cable I want to try...very expensive, but I think it will improve the sound. All in all, the best stage piano out there at the moment. Heavy, yes. Expensive case, no doubt. But it's the sound that counts. I move the piano, two amps, seat, heavy stand, microphone, cases of electronics and music all in a Honda Pilot with room to spare.