#10 doesn't ride "upright" in the summer months, I have no misgivings that he will do it in the winter months. Ouch, sorry #10!
I could see this thing only working in exactly the conditions shown in the video. hard packed on a hard surface. The video they went onto an existing moto-x track with 6" of fresh powder to make it look like they were riding in lots of snow. I think that skinny little track would just dig a hole to china upon releasing the clutch lever.
Could be cool on a groomed trail, but then again, why? And God forbid you have to make an evasive manuever.
But in the end, #10 is right - I'd love to try it!
The old stick in the mud skiers and ski resort operators had the same attitude about snow boarders. Think of the pluses. Same motor and frame for all four seasons. With global warming and all, this may be the future.