I've had my G3 since July. I have never used a case or anything on it. Completely nude. I handle my phone daily and often.
None of the color has faded or worn off anywhere on it (I have the silk white G3). The buttons on the back are not painted silver, they are pure metal. But I cannot speak for the black G3 as the button is surely painted black and may wear. The silver trim on the outside looks as it did when I first got it.
The body seems pretty strong although cracks from a manufacturing defect are apparent on the top by the little hole and the microphone hole at the bottom. If that matters to you at all. It's purely cosmetic, though.