I am running without badges, too. Its just more stealthy and you can "flow" with the other normal A6's pretty nicely...but can push it any time. Also makes alot of fun to scare some porsche drivers
And last but not least...potential idiots (i.e. thieves, vandals) cant identify easily your high $$$ valued car.
As for the US it maybe makes more sense to run the badges...otherwise probably only 0,000001 percent of the population will recognize the car...