Originally Posted by BluesDawg

Bombadil will pull out some meaningless study showing statistically that clipless pedals don't do anything to improve performance, but you will probably find, like most of us who use them, that they help you transfer more of your power to the pedals. The biggest difference I notice is on climbs, where the ability to apply power across the bottom of the stroke and possibly some on the upstroke will help you keep your cadence higher. I also notice a big difference when accelerating on a flat section. With clipless pedals I am able to more consistently spin circles rather than jerky rotations with most of the power in the downstroke.