Possibly the issue is, how well does the PSR keybed hold up over time? If several users are noting an improvement in the S910's keybed, but Ian (our resident PSR expert) claims no difference, it is fair to assume they are noticing a difference between what they HAD and what they now have...
Key wear can have several causes, but obviously, the first is likely to be force with which it is played (followed by how much smearing and glissing you do on it). If you come from a piano background and DON'T adjust your touch drastically to the PSR's ultra-light feel, perhaps it is not standing up too well to this? There are too many reports of 'better feel' from a new PSR keybed to discount this, I think...
By the way, just to earn the same fee from Roland as you guys are getting from Y&K (
), I have to say, I have a G70 that has been gigged almost every day by a pretty hard player for five years, now. And I just bought a backup G70 that was virtually showroom, VERY little use. I cannot tell the slightest difference between the two's actions. Pretty good, in my book. Admittedly, after over ten years on my G1000, I thought the G70 felt a little stiffer, but only marginally.
You get what you pay for... (unless you are a WS player, then you get BETTER than what we pay for!)