For someone like me (and I am not at the point where I need the card right now and can work around it), I think this is very fair to everyone. I can spend all day in the park, I just have to pace myself, take some time outs, stay out of the sun for long periods of time and keep hydrated. This is something I have to do every day of my normal life anyway so no different at Disney for me.
But as was pointed out earlier, I think this is going to be very hard on those that can only do a few hours due to a disability. I can see where if someone can only spend 3 hours a day in the park in the morning, go back and rest and maybe come back for a couple of hours in the evening, that they will unfortunately not get to do much as far as rides and shows go if it's busy and wait times are long.
Again, not blaming Disney...they are trying. I blame the abusers.