The 3rd video clearly shows that both the player as well as Yamaha have no clue what modern dance music should sound... Just listen to some trance of Armin V Buren or Tiesto and then compare it to those styles...
This implementation of the feature is not what will sell these keyboards to new users..
Bachus, I've heard both DJ's you've mentioned, and I agree that the PSR-S970's Dance styles and demonstrator fall short. However, I think that if someone wants to sound like those DJ's, then they should use the same equipment, and not an arranger keyboard.
In my case, I'd love to get an arranger, probably the S970, but those Dance styles don't interest me, so it doesn't matter.
I'm just glad they finally put some good choir sounds in there, and judging by online demos, it sounds very good. Now, for those of us who want a Tyros but can't (or don't want to) afford one, the PSR-S970 comes pretty close.