I know it's been talked about a lot, nevertheless I would state that just because PSR's keys are so light doesn't mean that they are bad.

I played a lot a decent Yamaha grand piano at a restaurant, my set was up to 4 hours, and I enjoyed that, but at home I had PSR-3000 and I enjoyed it as well and my fingers were adjusted to both units.

Keyboard can be called bad if it's unpredictable, so you can't get adjusted to it.

Right now I have Juno DS 76 with rather tough keybed, I had to get adjusted to it as well, perhaps, a week or so. I must say, that if I feel lazy (like late at night) subconsciously I reach for light keys, but after all, if the sound inspires me, I forget about a keybed.

I think Yamaha had to have enough arguments to justify a purpose of SX700/900, so they made a small change (as I understand, the same keybed was used in MX49/61 years ago), but they used that light keybed for years because it was actually just fine, it just takes time if you are moving from something different - yes, at first it's rather uncomfortable.