Cool, I also play with the Original Xbox controller on my PC. Yeah, the black button is a little awkward, but I have equal problems with a PS2 layout since I am not confortable using two fingers on R1 and R2 (I usually juist use my index finger to work both buttons at the same time, but if they are spaced far apart it can get tricky aswell.
Also, PES6 had a Longpass + R2 function for making longpasses higher and potentially longer. Also hard to use like controlled shot. I could use it on the Xbox controller, but it required some finger dexterity.