Whoever pilots that thing will be one of 2 things: the guy with the biggest balls in the world, or... a stain on the back of the cockpit!
Wasn't that the vehicle used in that "Buckaroo Bonzai" movie?

Is the rocket just a glorified version of the "over-thruster" from same movie?
If we already have planes that can break the sound barrier, what possible good will we learn from having a car do the same?
Maybe it'll give the car manufacturers a gimmick for the 2012 lines.
You know, REAL muscle cars, powered by rocket fuel, not that sissiy petrol that the "regular" people use.
Frankly, I see three possible different scenarios with this rocket-on-wheels:
It blows up on ignition of the "big" engine or....
it plows into a mountain, hillside or some other structure because they didn't plan on stopping it, just getting it to go, or......
It pulls a Wiley E Coyote and blast off into orbit.
Love that ACME rocket company!!!!