I have the centric binding on my 10EX's and like what it dose for the ski. I have a friend in NY that has the centric on G3's, she just made her PSIA II. I will ask her her she likes them. She was hard to talk with all last season, she was focused on making level II. I don't think she played much with the binding.
I know what you mean about haviing the skis in different settings. I skied the Blow Hole at Blackcomb with the bindings in different settings, (2 & 3). I didn't noticed anything strange. But when I have moved them to the back on powder days and forward on firm days, I can tell the difference. I can also feel the difference in the Marker SC bindings. I know some people say they can not tell the difference in the SC either.
I have also skied a buddies K2 Mach S with the piston, I noly skied them with the piston on, I felt they made the ski very stiff. I skied his other pair of Mach S's with the SC binding and liked them so much I didn't want to give them back.
I'm kind of leaning towards the Piston for my AX3's, but I have time.