Spec-wise it seems roughly equal to the PSR-SX600, maybe better in some ways. If it does sell for $800, you're getting a LOT of functionality for that price!!
The "Adaptive Style" feature is interesting. I don't recall seeing something like this on a Yamaha before. If you play more notes, or "harder" velocity, the arranger engine picks up tracks from a more advanced variation. So when it's active, you have thirteen fuzzy variations instead of four discrete ones. Pretty slick!
I could probably approximate this on my Roland with an expression pedal, some MIDI Solutions black boxes, and a whole registration bank filled with subtle variations of the same style. But I think Diki would tell me that my setup is too complicated :-) Honestly I'm jealous, it would be a nice feature to have!