Believe it or not, I see one of these Street Striders many evenings used a commuter vehicle.
I think the benefit of something like this is supposed to be a more complete workout. The Times Gear columnist who reviews these products, Roy Wallack, is a fitness freak, runner and cyclist, so I'd think he would know that aerobic capacity is what limits his speed and endurance when he writes about how using his arms is like "you're on a regular bike with an extra motor." If you can't get more oxygen to your guns, it doesn't matter how many motors you have or how big they are.
Via bike business consultant Rick Vosper, who tweeted, "The LA Times showcases four bikes you definitely don't want to see under your Xmas tree. Or anyone else's."
That looks like a way better upper body workout then being in a gym with sweaty, communal machines.
Little known fact- you get a better cardio workout with your arms than your legs. Professional orchestra conductors have hearts the size of Olympic athlete's hearts from all of the arm movement they do.