Yeah, ball of the foot. You can change around and go a little in front or a little behind to work it a little differently, which I actually kind of like - against the one-position-all-the-time of my road bike set-up.

Ankling is good for accelerating, like up a hill to a fast-changing light on one intersection I go through at least twice a day. I imagine if you tried to do it all the time though you'd wind up with some screwed up joints.