I hung on to my 5S for the longest time before finally getting an 8. I'm happy with the 8's form factor, but it's definitely at the upper limit of what I'm willing to carry around in my pocket all day. I can operate it with one hand, though sometimes a little awkwardly.

I hated not having the headphone jack for a long time. But AirPods (which I do love) have taken care of that problem.