Having initially started this thread and getting sidetracked into purchasing the Yamaha CP4 stage piano I thought I might leave you with my conclusions. First and foremost: I did not keep the CP4 as it had a substantial trial-period, not that I had to think long and hard. In one word: nowhere did I get even close to the WOW factor.In detail:
I know it is unfair to compare it to my old (2001) Ymaha P80 stage piano but more and more I am beginning to understand why the P80 is such an icon among stage pianos.

The CP4 at approx. 2000 euros harbours three basic piano samples , only one them a new one and not particularly impressive. The internal programmable memory holds 128 Performances whereby each basic piano sample is stored in 15 different manners with 15 different names. Nice marketing but pretty senseless as you can make your own performances by altering the key parameters such as filter, resonance, eq, envelop etc. Ultimately you are stuck with the three basic samples and like I said one of them is very good but hardly different from the one used in its predecessors. The keybed is an improvement on the CP5 in that is graded and of course also wooden keys. Probably out of habit I still prefer the superb keybed of my P80. the CP4 furthermore boast a few hundred sounds derived from the Motif workstations, some useful some less useful but of minor importance when looking for a good acoustic piano. So all in all I thought 2000 euros was a large amount of money for a, for me, minor progress.
Later on this year I will give the Roland FP30 and Kawai ES110 a go but for now I have other interests, both musical and non musical.

regards,
John