There used to be a guy in Cheltenham who had one, I saw it quite often, but he always seemed to be going in the opposite direction, so I never got to chat to him. He moved along at a fair pace, the equal of most good cyclists.
If I remember correctly, the arms can provide almost as much energy as the legs, so someone on a hand cranked cycle is not significantly worse off than a pedal powered vehicle.
What doesn't work is trying to simultaneously arm and pedal power a cycle. The human body can't provide enough energy to do both, so the additional energy gained is more than compensated for by the additional mechanical weight, ie you tend to find it makes things harder!