Just came back from the Apple Store so I figured I'd give my impressions.
First off, best black is Jet Black. It looked great and especially felt great. The grip on the smooth finish feels so much better than the standard matte finishes... provided a much more confident grip. Keep in mind this was a standard 7, but I figure the same improvement would be true for a 7 Plus. In terms of looks, it looked more premium, even with fingerprints all over. The fingerprints didn't bug me much. And it seemed more durable than I imagined. I couldn't detect any marks or blemishes on the finish despite being handled by random people all day. So if you are the type that typically takes good care of your phone, I don't imagine you will have an issue. Anyway, based on my impression from tonight, I'm planning on going for jet black and sticking to no case/skin like all my previous phones.
In regard to the home button, I was indifferent about it at first, but it grew on me after playing with it for a bit. So much so, that my regular iPhone 6 clicky button felt weird in comparison after. The thing that makes it different to me is that the clicking-feel is felt by the portion of your hand that is holding the phone, and not your thumb. With a traditional clicky button, the click is registered or felt by the thumb and not the hand. This one is reverse. And because the click is felt by the hand, the feel or intensity of the click was really dependent upon my grip. As the phone changed positions in my hand, the click intensity would appear to change due to how tight my grip was, lending to an inconsistency in the click feel at all times. I noticed if I placed the phone flat on the table and attempted to press that home button (which I sometimes do if I'm eating and reading from my phone), I could hardly feel the click. It clicked, but you just couldn't really feel it since your hand was not actively holding the phone. If you had a nice solid grip on the phone, that's when the click felt best.
Also I tried the two cameras on the Plus as well. I tried covering up the lenses like other people had mentioned. I couldn't quite figure out what was going on but it seemed to be using both lenses. I could cover one lens and clearly see the screen toggle between the two (blocked and unblocked on the preview) when I toggled the 1X/2X setting. (Which clearly shows that you are toggling between the two) However, when I attempted to cover the other lens, it always showed an image despite the zoom toggle position. It's like it uses a aggregate of information from both lenses for the preview with a priority on the info from the wide angle lens. I figure this allows them to maintain a smooth zoom transition as you increase the zoom from 1X to 10X using the slider and prioritizes information from the fastest lens with the largest aperture. I'm sure more details will emerge over the weekend.
Anyway, that's it for now. Jet Black 7 here I come. (Trying to resist, but the trade in deals right now are too good to pass up.)