I only really enjoy playing solo piano on an 88 note weighted hammer action keyboard...I use a Yamaha P85, soon to be replaced by a new Yamaha KX8 controller.

Having said that, and with piano being only one of the many sounds I use on an arranger, the action just needs to be velocity sensitive and no more than 5 octaves.

I dislike semi-weighted actions (especially with aftertouch) such as found on the G70 or Tyros.

The light quick action of the PSR-S900 is ideal for my purposes, as most of my gigs involve arranger play....velocity sensitivity is perfect, going from no sound when pressed very slowly, to max when struck quickly....just like a piano, actually.

Key action is a very personal thing...if it doesn't feel right, then it is sure to affect the time you spend playing, as well as how you play.

Ian