Hey Chony, not to jump on the "build quality/button durability" bandwagon, but I've owned my PA1-X for the better part of a year (gigging professionally every week-end and some mid-week dates - and I play some very Hard Rock n Roll/Bar room piano at times) and there's been no button/build problems for me in the least.
One thing that DOES bug me about Korg - well, more specifically the PA1-X.
The damn touch screen (and general speed of the keyboard) can be pretty damn slow and unresponsive.
Is the PA2-X screen more responsive and is the Board generally "faster" than the PA1????
(Maybe Dennis can answer that question....)