Interesting, I never fetl it was worth doing a yearly upgrade (obviously others disagree YMMV etc. etc.) and that's fine. It seems that battery life at least for the other posters is greatly improved. I went from a 6 (albeit a replacement with a still good battery) to a 7 + and noticed a huge improvement.
While I'm still on the 6S, I have a friend who went from 6+ to 7 and he is not impressed with the battery life. Before he would have 10-20% by the end of the day, and he says now he usually has to plug in at some point in order to make it until bed time.