General
It is a very solid instrument with all metal panels. Not very heavy for such a robust stage piano at 18kg. Slightly better than those 22kg digital pianos. It's also good-looking, kind of vintage due to rocker switches, etc. I like that they put the pitch and modulation sticks above the keyboard and not to the left as on some other stage pianos, thus it's not too wide.
Interface
It's very easy to use, similar to a Nord interface, almost no menu diving.
Keyboard
The keys feel nice and heavy. I've been going back and forth between it and my Yamaha AvantGrand N1X and the CP88 feels slightly heavier and just a bit more pushing against your fingers compared to the real grand piano action. But difference is not huge and I felt comfortable going between both instruments. It's not a tiring action to play, nor is annoying in any particular way. What is more, it doesn't have artificial escapement simulation and that's good since I find those fake escapement simulation notches really unnecessary! It's a graded action and has wooden sides (cores?). The touch response with the piano sounds is very good. I previously returned a YC73 (with BHS action) before getting the CP88 and I think the BHS action was less heavy and was also easier to play but somehow springy (pushing back against tour fingers all the time) and the BHS also had some plastic feel to it. With the CP88 I there's more realistic hammer feel beneath my fingers. That is all subjective but I can say the NW-GH3 action is definitely a superior action compared to the BHS and is probably among the best digital piano actions I've tried.
The white keys have some fake ivory surface to minimize friction. I'm not a huge fan of those. But my skin is very dry usually. Maybe people who sweat a lot will find it good. The black keys have artificially roughened texture and I find this rather silly. Maybe some people love these things.
Sounds
This is a professional stage piano for gigging musicians, not acoustic piano replacement (or home piano), so take that in mind when reading my review.
All sounds are really sweet and nice. I went through all the factory programs which include various acoustic pianos, electric pianos, as well as various layers with pads, organs, synths, etc. and there wasn't a single one that made me think "this is cheap, why did they put it?". I'm usually very critical about layered pianos with pads and strings but I guess the quality of the samples and effects is pretty high here because none was annoying, they are very subtle and varied and many of them reminded me of sounds I've heard on Lyle Mays records. It's definitely been programmed by real musicians who use these programs rather than engineers.
As of firmware 1.5 there are now 6-7 full different acoustic piano samples with the CFX naturally being my favorite, I'm used to that sound already. They recently introduced a Hamburg (presumably Steinway) which is also very nice. There is a "Nashville C3" sample which sounds realistically imperfect and thus suitable for non-classical piano work. When I say "imperfect" I don't mean honky-tonk, rather a piano that is more real life, like a good workhorse (non-concert size) grand piano that you would find in a studio. And it's not an exaggerated piano sound that is artificially brightened or something like that. It's just a nice Yamaha studio grand piano sound (I think Nashville is the studio where that piano was sampled) that can find great usage on stage and in more pop/jazz oriented context.
There are also a few upright pianos and the recently added felt piano in 1.5 is absolutely fantastic! Especially combined with the excellent reverb and compressor it's a nice sound for modern cinematic/pop stuff.
There are so many Rhodes samples and all of them are excellent. The effects and the amp simulation are too. Enough said.
The pads and strings are all very nice. Jazz organs are OK I think, there's nice rotary simulation. Maybe not for purists but usable.
All the effects sound great. The reverb is a high quality one IMO. Not to VST standards but better than the average for professional stage pianos. And light years ahead of the usual reverb in home digital pianos.
Features
It has a USB interface, so I can easily add Moog Model D (and other iOS synths) to it through a single USB cable to my iPhone (for both MIDI and digital audio). It also has a very good master controller functionality with 4 external zones with detailed settings (including program change), so one can prepare live sets that include external synths.
Another "feature" is Yamaha have IdeaScale where people can suggest features for the CP/YC (and other instruments) and they listen to the customers and implement some ideas, constantly improving the usability, adding samples and features. Seems those instruments were created as platforms that can be constantly updated and enriched and that is rather surprising when you consider it's Yamaha who are the last company you could expect that from!
Cons
It would be great if there was VRM (virtual resonance modeling) as in their Clavinova and P515. There's only damper resonance effect here which is rather subtle but as I said it's a professional stage piano for gigging and not for home situations.
I'm not sure if it's a bug or feature but a few of the encoder knobs have less resistance compared to the rest.
If you wonder about a piano bag, I can confirm the "Gator GKB-88 Slim" is a perfect fit and a very robust and well made case with internal straps that hold the piano tightly.