I use my left hand for almost everything, except when the CP layout dictates otherwise.
Tron needs the stick on the right to feel proper, for example.
I will fit the CP to my taste however.
I play Tempest with the spinner on the left, where I think it SHOULD have been in the arcade.
Trackball games really depend.
I play Missle Command with the trackball to the right, and Centipede/Quantum with it to the left--most of the time.
I can switch up if it's already in one position or the other, and I don't feel like switching it.
I probably should mention (if you hadn't guessed already) that I am naturally left-handed, but highly ambidextrous.