Ian,I know of at least 3 "Pros" using WK3000's, and two others that are going to get a WK...The main incentive is a light backup, but all are impressed with the organ drawbars and pianos..
BTW, each of the Pros own 1/SD1...2/PAx1...3/G1000[me].....and soon to be: 4/PSR3000...

The Casio WK can not beat out any of the above boards, but sounds for the price in a lightweight package and 76 keys...$ for $ it may beat out all of the above..

Don't get me wrong ...No one is going to dump a G1000,SD1, PAx1 or even a PSR3000 for the WK....[well maybe the PSR]..