Sound quality and limitations aside... this is the first time I know of that Casio has given users the ability to create styles from whole cloth. I am not sure if the styles are compatible with the PX-330 (which does have good sound IMO.) If so, PX-330 users who are tired of the factory styles might buy the CTK-7000 just for its style creation capability.
Casio allowed you to record user styles from scratch on the MZ-2000 (and that board was like 10 years ago). This new line of WK models are heading back in the direction of the MZ-2000. However they're a more watered down version of it. The sounds on the old MZ (that used the ZPI sound chip) IMO were better than the current WK's.
These new WK's also don't have anywhere near the tone editing capabilities of the old MZ. Still.., I may pick up a CTK-7000. If the WK-7500 is going for a mere $499.., then I wouldn't be surprised to see a $399 price tag on the CTK-7000. I think the CTK-7000 is going to be a very good bargain arranger with features found on higher end models. Even at the $499 price tag.., the WK-7500 does a hell of a lot for the price. You're getting full style sequencing, 16+1 Midi Sequencer, Drawbars, SD storage, and the BIG whammy IMO is the audio recording feature.
Granted the sounds may be sub par to what's out there now.., I think behind the right hands these new models can sound pretty good. If I get the CTK-7000.., I without a doubt would probably use every bit of the tone editing and DSP editing to clean up the tones. The editing is limited..., but if used creatively should yield some pretty satisfying results.