I can't for the life of me figure out why this is supposed to be an improvement on a chain drive. One of the main reasons pedaling is so efficient is that the motion is basically slightly modified walking/running--our legs are evolved to come down in front of us and lift up behind us. This substitutes a motion where the downstroke and the upstroke are in the same position. Given that I can't think of a single human activity that involves doing this under load for extended periods of time, I have to suspect that this is going to create some unanticipated problems, but even if I'm wrong about that, is there any reason to expect that this motion will be any easier than conventional pedaling?

Mechanically, this is a dual drive vs. a single drive. I can't believe that a dual drive won't be heavier and more prone to failure just due to complexity.