That's a big reason I got a supermoto: Getting around town and splitting traffic on the bridge. And dude, your bike better be faster than 100 mph. I get close to that on my DRZ and it's only a 400 with crappy aerodynamics.
Anyway that thing looks like it would be fun for a couple hours but after that I'd probably wish for either a real moto or a real DH bike.
I want to get some wheels/tires for my YZ450F.