Pale Rider
Legendary Member
The treadle drive is more like a "stair climber" in use. Takes a bit of getting used to.
The Elliptigo is sold as a serious treadle bike.
Riders - if that's the right term - have done London Edinburgh London (LEL) and Paris Brest Paris on them.
I saw one at the Barnard Castle control of LEL - he was the only competitor who didn't have to take off his shoes to preserve the floor of the control building.
http://www.elliptigo.co.uk/#