Bought a set of Uniroyals from the local Chevy dealership, which installed them - pretty bad vibration. And the paint marks weren't mounted anywhere near the valve stems. Went back, told them about the imbalance/paint marks, and after the service advisor (the guy that receives the car, whatever he is) tried to tell me he'd never heard of paint-mark-at-valve-stem and that it didn't matter, they remounted and balanced them and they're fine after 50K.
I don't do tires at my shop, but when I discuss new tires with customers I always tell them if there's any imbalance go back to the installer ASAP and tell them to make it right. No excuse for anything but buttery smoothness from a new tire.