The one iPhone feature I want back isn’t the headphone jack — it’s this

Peek and Pop was a brilliant UI paradigm that combined different levels of finger pressure with haptic vibration from the fantastic Haptic Engine linear vibration motor.

It allowed you to firmly press on content, like a link on a website or an email in your inbox, to "bring forward" a small preview. Then, with a firmer press, the content would fill the screen. It was a more natural way of looking at something without leaving your current activity, then letting you jump to it with a natural gesture.