In short, I had a black 256GB iPhone 7 (AT&T) for no more than a day because it ran excessively hot, even while off charger and not being actively used (screen off). At one point its surface temp on the back casing was 112F (via IR thermometer) in a 65F room. By comparison, my wife's 32GB phone was 75F at the same time. At the time of this writing, I have a replacement phone (128GB) operating at 76F. (Screen off, not plugged in, doing nothing.) I understand when the phone is first fired up it's going to run warm while iCloud stuff is going on; indexing is going on; so on and so forth (I did no backup restore -- set up as New). While at work today (18 hours after phone initialization), I charged up the device to 100%, unplugged it and let it sit with no usage except an occasional iMessage or SMS reply. The battery was dead in less than 6 hours. I have DFU installed 10.0.2, left it sitting at the hello screen with SIM pulled and no WiFi -- 91F. Clearly a hardware issue on this device. I spoke with one of the reps at the Apple Store when I got my replacement and he claimed a family member with the same iPhone 7 256GB talked about it running much hotter than expected, but made no statement about battery performance. Curious how others with the 256GB 7 (not Plus) are faring with the thermals.