Squeak, what I look for in a piano....a good tone in the bottom and mid range[usually where they falter] ..Also the high end has to be crisp without the electronic sound..
As for playability, velocity[touch response] has to change the tone when hit hard...not just get louder[this is the biggest problem with most, and I am not going to name those guys again]..
It also has to have a natural decay....

My favorite piano patch[in an arranger] so far is the Roland E-600..
My favorite in a non arranger is the Roland RD700[new model]..
I haven't heard live the G70[favorable opinions], or the Tyros2[said to be the same as the original Tyros]..

The Casio[I have the WK3000] isn't bad, but I think it is thin....more like a rock piano [brightness].