I have two concerns:
1) They still haven't fully eliminated the sudden shutdown behavior. My old 5S would shut down randomly under 20% without warning. Sometimes it would make it all the way to 1-2%, but most of the time it was between 5-15%. You'd think they'd scale performance throttling untilt this wasn't an issue.
2) I think their messaging with respect to battery health and the battery being a consumable is pretty poor. As far as I can tell there's no built-in battery health indicator in iOS. Sure there are those dodgy "Super Battery Health Plus Pro" apps, but it seems like a diagnostic menu in settings would go a long way. Even more puzzling is that techs at the Apple Store have access to some sort of diagnostic that does this already. Last time I went to get another issue fixed the guy said that my battery was at 70% capacity and the voltage was pretty low. Why wait until '2018' to ship a self-serve version of this?