I have had the Jet Black 7 for about a month now. Whilst I waited for the Nomad Leather Case to arrive, I placed my iPhone in the Siena leather sleeve that I had for my 6S. Because of the slightly different dimensions, the sleeve was a bit of a tight fit. Turns out that pulling it out of the sleeve and putting back in multiple times a day caused many micro-abrasions, and placing the Nomad case on caused scuffing on the bottom. Both had a microfiber lining. Thankfully, the markings are not at all noticeable unless caught in just the right bright light (i.e., held underneath a lamp).
So I’ve been going caseless ever since (particularly since I bought the Jet Black because of the finish). I work at home, so I normally keep it resting on a microfiber cloth (the black cleaning cloth that came with my iMac) most of the day and place it naked in my back pocket—I never place anything else in the pocket with my iPhone—when I take the dog out walking. For the last week I’ve kept it out of a sleeve/case, I haven’t noticed any new abrasions/scratches. I wanted the Rose Gold 7 before the keynote but now Jet Black is my favourite colour/finish. It’s beautiful (especially when under normal lighting, where none of the abrasions show up) and the grip is the best I’ve experienced with an iPhone (the 3GS was my first and I’ve bought a new one each year from the 4S on). For comparison, my 6 and 6S slipped out of my hands consistently (my 6 was especially scratched from several drops onto the ground). I’m OCD about damage to my iPhone—both because of personal preferences and my desire to keep a high resale value on my iPhones—so we’ll see how I feel about going au naturale after several months, but currently I coudn’t be more pleased with the Jet Black finish.