Another problem I had was that after updating my iPhone 7 and trying to restart it I received an error 4013. I had to restore as new then install a backup to get my phone back to working again. The same thing happened when I updated to iOS 10.2. Took about 4 hours to get it back to where it was before the update. I won't know anything about battery life for a couple days as the phone was connected to my computer and charging much of the afternoon.
Regarding Battery life with iOS 10.3, I see no difference with my iPhone 7 after going to 10.3 I charged the phone overnight and have been using it for almost a solid 90 minutes since I got up and it is still at 94% which seems about normal or slightly better. I haven't found any other quirks yet.