My iPhone 7 gets phenomenal battery life compared to my 6s. When I first get an iPhone, I always like to run the battery down to 0% the first few days to calibrate it. Even using it a lot the first few days, I struggled to get the battery life below 30% by the end of the day. So I had to do a bunch of slow-mo recordings with the flash on with the screen brightness set to max. I'd then stop the recordings and start a new one while iCloud uploaded the recordings in the background over WiFi. The iPhone 7 got pretty warm but it took a while to run down.
What I've definitely noticed is a big improvement in the last mile of battery life. Sometimes my old 6s would shut down just below 10%. Maybe there was something wrong with the a battery cell? Either way, I've owned most iPhone models, and the last 6-7% would drop so quickly and die out at 2-3%. My iPhone 7 can hit 1%, which is interesting and sounds logical but I haven't really seen that before now.
In day-to-day use, I rarely ever have less than 20% left, often have more than 33% left, and a few times have had 50% left when going to bed. This is a huge improvement, and is most similar to the battery life I had on my iPhone 6 Plus which could sometimes make it through an extra day without charging. So not quite that good, but pretty close for a 4.7" device. I'm really hoping that those newly developed lithium battery improvements come to the iPhone next year. It would enable them to make the iPhone thinner and lighter, while also increasing battery life to two days of use. They should also get a boost from shrinking their chip process next year.