Just wondering if it affected hill-climbing?
[Sitting] DF riders "rock" while doing hills - I think "rocking" allows them to keep a more constant velocity between pedal-strokes - improving their efficiency during the climb. Going up hill, if we slow-down between strokes, we speed-up (accelerate) on the next, and energy is required - lost - just to accelerate, in addition to the work required to go a few feet up hill. Does an elliptical chain-ring help keep a constant velocity going up hills?
"Rocking" example: http://www.youtube.com/watch?v=OzIxObE2A0U