So I just got the PX-S1000 and tried it out... and its nothing short of amazing in just about every respect! As Casio has been saying, everything about it is new: new case/chassis, new key action, new samples, new sound chip, new user interface, etc.
Two things in particular that I like are the key action, and the deep, rich sound in the lower register of the piano samples.
So I did a video where I played Queen's "Somebody To Love" to demonstrate what the sound is like:
I'll do a full review after becoming 100% familiarized with the board.