I upgraded and the same thing as with every major Apple upgrade: Battery life is horrid. The two best features is the scanner ability and QR code reader built in.
One would think Apple would address that above all else.
If anything would get people to buy a new iPhone, a longer battery life would!.....................
Try killing applications in the background, and reducing the brightness of your display. I find the battery life on the 7+ and the previous ones, very exceptional. But having lots of applications and a very bright screen, do impact performance.