Pressure, or aftertouch triggered actions are a bit of a problem for me. Because I also play piano, my touch is a little on the heavier side than many arranger only players, and having things like fills or part switching happen in response to aftertouch leaves me at the mercy of accidental occurrence, when I play loud...

It might be better if there was a control that allowed you to set up the aftertouch trigger VALUE, so that only the heaviest of pressure would trigger it, but so far, most of these things will trigger even at low to moderate pressure. Play a big horn stab, or a fortissimo on the piano, and next thing you know, the damn arranger's taking a fill!