The key feel on the Casio WK3500 is great. On a Casio!!! There is no reason (other then greed) for Yamaha not to match the Casio quality of keys.
Bluezplayer said, "I thought that the 2k's organs needed updating too". The PSR1500/PSR3000 are to have organ modeling. We'll see if that makes a difference.
Starkeeper