Piano people are a conservative bunch...
Most acoustic piano advertisement you see, every one likes to claim some sort of history going back to 18xx, every one likes to claim "old world craftsmanship," every one likes to claim "we're doing it the way it has always been done in the last xxx years," every one likes to throw in the word "hand-made."
NO ONE wants to claim "we use the latest and greatest design innovations," "we use the latest and greatest manufacturing technique."
Kawai took a huge risk going the way of ABS (and now, carbon composite with their Millenium III action). Every once in a while, some one would come onto the Internet asking about this ABS (and now, carbon composite) issue, and they would very frequently describe how they have been told all sorts of "bad things" related to "plastic parts" in pianos. And people like Brian Lawson and KawaiDon would have to jump through the hoops to assure these nervouse shoppers that indeed the ABS/carbon stuff is really a "good thing," or at least there is "nothing bad about it."
Being in the deeply conservative and deeply traditional piano industry, this is the kind of market reality that Kawai has to face, this is the kind of risk that Kawai has to take to introduce something dramatically new and different from all other major manufacturers of pianos.
Looking at it from another angle, what reasons are there to continue to use wood as moving parts except for the fact that that's the way it has always been? Some one made this comment before: The piano is about the only industry left that uses wood to make lots of tiny moving parts, no one else. Why?
I do wonder if Kawai's upper management ever second guess their decision to have gone ABS every few months.
From personal experience though, when I first played a Kawai grand with ABS action, I couldn't tell it was not wood until some one told me. I observe other pianist friends play them... again, they couldn't tell the action is not wood until some one told them. So I'm quite certain that most pianists cannot feel the wood/ABS difference by playing the pianos.
The rest of the issues would than be a matter or science: is wood/ABS/carbon easier to maintain, is wood/ABS/carbon easier to manufacture to tighter tolerances, is wood/ABS/carbon cheaper to produce overall in small/large quantities, is wood/ABS/carbon more dimensionally stable in most usage scenarios and piano storage environments, is wood/ABS/carbon more capable to resist wear under heavy use over the years, etc.
Good luck with your research.
