I have a cell phone but I've never owned an iPhone. My biggest complaint is that they no longer have removable batteries.
Removal used to be easy, a matter of opening the back, popping the battery out, and putting another in. Now the battery is affixed to the phone with attached power leads, and some are locked in, and how easy it is to remove depends on the make of the phone. When I traveled I used to carry a charger with an extra battery for emergencies. That's not so easy anymore because the phone is the charger. I have a portable charger bank that will work if the battery is still good.