I use the expression pedal for pitch bend on the PSR-3000, you can assign it to R1, R2, L, or all three. I use R1 only for pitch bend for obvious reasons. You can also set up the amount of the bend in function/controller. You can save the setup with an appropriate right hand voice in a registration for instant recall.

I also use the expression pedal to 'kick in' the leslie effect on certain organ voices, and again save that setup to a registration.

I'm sure there are other ways to use the expression pedal, other than for volume expression...who does that?