It looks pretty unstable and dangerous to me too. Looks like you'd land right on your face if you had to suddenly brake.
Illegal to ride it on most city sidewalks....and if that guy were to pass lots of cars on the right in traffic, he's gonna get creamed. I can just see him slamming broadside into a cab running a red light in NYC.
Maybe they should have named it Yikes!. LOL If I wanted to avoid pedaling, I'd feel way safer on a scooter, which would get about 90 miles per gallon.
It's a cool 'concept', but maybe best for places with no cars or hills or bumps or.....