Brake Disc Caliper problems of the 2012 Chevrolet Silverado

This truck has chattered, hopped, and had bad brakes as soon as we drove the truck off of the lot. When we went with the dealer who sold us the truck, my husband said why is it vibrating & he told us that it was in the tires from "sitting". It has had 2 new wheels & numerous brakes, pads, rotors, calipers, drums. & it still vibrates. The dealership has even put another trucks tires & rims on the truck & it still vibrates. This is unacceptable for a new vehicle. When I called the gm district specialist on 5/29/13 she told me that the vibration & hit & miss acceleration was a characteristic of the truck. $40,000 truck & it is not a very good ride.