I have a black raven ATS. My prior car was a black Merc C300 (09). This mini-review comes from someone who lives in a cold state (MI) and takes extremely good care of their car.
I have hand washed most of my cars, with few exceptions. My '09 Merc C300 saw only two machine washes, and then only three years of ownership. My ATS will never see a machine wash.
Within weeks of owning my Mercedes, I could see significant swirl marks. Not so with my ATS. After a harsh winter (I picked up my ATS in early January) I made a thorough spring washing and polishing to survey the damage. GM >> Mercedes in the paint department! I am absolutely astonished how a car could go through a cold winter with so many washings and come out with virtually no swirl marks. There are some micro-scratches, but a round of meguiars machine glaze applied by hand gave me what is for all intents and purposes a factory paint job. The exterior paint engineers at GM are doing a hell of a job.
Well done, GM.