There are a number of posters complaining about battery drain on iPhone 7 on iOS 11. I certainly experienced it on my iPhone 7. However, taking it to Apple now they run diagnostics and tell you that the battery is healthy. I was advised to erase all content and settings, set it up as a new phone and come back if i still had issues as it was likely some sort of software bug. It was a very different experience to my last issue (with an iPhone 5) where Apple swapped the phone on the spot.
Beyond battery drain, iPhone 7 was my least favourite iPhone and I have had every generation since 3GS except the 5S. I found that bluetooth connections often dropped out, bluetooth audio (despite this being the wireless audio phone with no headphone jack) was much lower fidelity than other devices I owned. The LTE modem did not keep a data connection as strongly as my previous 6S+ did and the camera was barely better than the 6S+. I often felt like downgrading to 6S+ again with that phone.
I could've pressed much harder for a replacement phone but I was coming up to a point in my contract where I could upgrade to iPhone X and I did. Pretty near every issue is resolved - I still believe the 6S+ LTE modem is better in real world use. If I wasn't so heavily invested in the Apple ecosystem, based on my iPhone 7 and experience at the Apple Store genius bar, I could easily have decided to make a switch.