I guess it's a matter of personal preference, but I really like the "rubber buttons" and prefer them over the buttons on my old 3k and the ones on the Tyros2 I had on loan.

The rubbery surface is perfectly grippy allowing no slippage, and, although the buttons require a more positive push, it is a good thing since they are situated so close to the keys and accidental activation during a heated performance is lessened.

Haven't heard of any quality problems regarding the buttons here in Canada.

John...you're gonna love your S900...once again, congratulations.

Ian