i dont know about pa800, and i am not sure about pa1x, but i remember when i had the pa50 one of the things i didnt like was the rubber buttons. they were ok, but i didnt appreciate much the feeling, even though their action was correct (except for one of the OTS buttons, but never mind! )

and btw, a funny story: a few years ago i had a kawai fs630 keyboard. quite a good instrument for the time. i left it over night somewhere in a wherehouse, with no bag or cover on it. in the morning, i was very surprised to see the one of the rubber buttons were... eaten by mice! hehe, after that i had only half of button to press...