Thanks for all the great replys and the links. From what I am reading there is not much increase in efficiency to be had by going from platforms to clipless. It seems that the riding style and the terain may be the best argument for going clipless. In my case I ride on smooth surfaces and do not race so I can slow down for the occasional rough spots. A racer would not have this luxury and therefore would need the clipless system to keep his feet on the pedals.

If I could pick up a 10% increase in efficiency I would probably go with the clipless system but since I ride for exercise maybe I would be cheating myself out of a good workout. I know that the clipless system has some great advantages for many riders but for my relaxed riding I would probably have a hard time getting much use out of their advantages. Maybe one day I can get in good enough shape to justify the clipless system and then I can ride with some of the groups around here that don't want to ride slower than 18 mph.