I'll say this..., if they're soft rubber then I say "that's great".... The contacts on the PSR "dimple click" type buttons can be a little iffy. I've always found Yamaha's soft rubber buttons to far outlast the other type.
Squeak
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GEAR: Yamaha MOXF-6, Casio MZX-500, Roland Juno-Di, M-Audio Venom, Roland RS-70, Yamaha PSR S700, M-Audio Axiom Pro-61 (Midi Controller). SOFTWARE: Mixcraft-7, PowerTracks Pro Audio 2013, Beat Thang Virtual, Dimension Le.