I really don't think the touchpad is going to work as well as a mouse or a thumb-stick. After several years of iOS gaming I still loathe games which use an on-screen "gamepad" design.
They spent a lot of time in their announcement talking about how they know that model is terrible and how they've tried to address its shortcomings using haptic feedback. Presumably, the final product will be nothing like thumbing over your iPhone.
My issue with those on-screen gamepads is that I drift. There's no feedback about whether or not I'm centered on the dpad for example. It sounds like little nubs would fix that pretty well.
