For me personally Tom, I can play fine on any keys, obviously piano needs a more weighty feel though to be expressive. My issue is one of quality, over the years i've had a few Korg synths with the cheaper Fatar bed, and random keys either stop responding or get stuck at 100% velocity. When you are paying £1500+ for an instrument (which takes a lot of saving) you expect proper quality, otherwise you might as well make do with a £300 PSR. I wish Korg and especially Yamaha would realise this, and make a quality keybed a priority in their medium/high end range. I would never buy a PSR-S900 purely for this reason, although I think it's a fantastic board otherwise. I am probably just showing my age, I remember when everything was made to last, and a synth was built like a tank lol.