Wife's new iPhone 6s+ seemed to die. Wouldn't turn on until I did a forcre reboot with power/home. Looks to be a common problem. luckily it doesn't happen that often...
http://www.macrumors.com/2015/10/01/iphone-6s-random-turnoff/
<Rant>I don't understand how apple can release such buggy software and not get called out for it. I experienced a problem with iPad Air original release also, safari crash randomly due to poor memory management or whatever. Eventually they fixed the problem after 6 months or so. They have a small handful of devices to support, you would think they could manage to release a non-buggy OS. </Rant>
http://www.macrumors.com/2015/10/01/iphone-6s-random-turnoff/
<Rant>I don't understand how apple can release such buggy software and not get called out for it. I experienced a problem with iPad Air original release also, safari crash randomly due to poor memory management or whatever. Eventually they fixed the problem after 6 months or so. They have a small handful of devices to support, you would think they could manage to release a non-buggy OS. </Rant>