Safety concerns aside, other cyclists can't believe the power I can generate riding true barefoot on junkie Pyramid Barefoot Pedals. With infinitly variable stiffness built into my foot musculature (I'm a barefoot runner), no material to compress, and toes naturally gripping the pedal when in the proper position over the axle, I truly believe that the only faster alternative is a full blown cleated road shoe.
But those are what caused my arthritic foot joints to begin with, forcing me into barefoot activity as a result, so not an option for me!
Your Vibrams are probably ALMOST as good!