I would call it a S970 enhancement. About 100 more Voices, Mono Legato, save Arp parameters in registrations, more styles, and 50% more expansion memory, etc. This is just a teaser keyboard. If you own an S970 you will take a big loss on buying the S975 for just a few improvements. I recommend waiting for the next PSR (or whatever it will be called) upgrade after the S975 . I believe it will have even more enhancements / improvements.
Joe H