From the Ars Technica link I posted:
dougg3 said his setup only successfully completed the level 1 to 5 percent of the time, an oddly low success rate for a system that's supposed to play with robotic precision.... "What I found is although the actual electrical pulses I'm sending to the controller are exactly the same length each time, verified on an oscilloscope, sometimes Mario doesn't jump," dougg3 said.