i prefer S phones so i upgraded - but there are things i prefer about the 5S.
the design is better - don't care how old it is, it still looks way better than the 6/6S. the size is better in my hand - i have smaller hands, so using the 6S is really stretching out my fingers.
Everyone says the cameras on iphones are so good, but my 5S is just as good as the 6S - a bit dissapointed in that. but with a 1 year old in the house, the live photos are awesome, so that makes up for the mediocre photo quality.
I'll upgrade again in 2 years to the 7S..
on a side note, i bought my 5S second hand about a year ago for $450, and I sold it this month for $400.... $50 for a year of iphone use (albeit 1 year behind the latest) is pretty reasonable.
My wife will be sticking to her 5S til it breaks down in some way, that's what she did with her 4S. She complained about the size increase from the 4S to 5S lol
My father bought himself an iPhone 5s last week. And coming from the 4s, it's a huge upgrade to him. Still pretty fast too. Apps load quickly (most basic apps load as fast as on my 6s), and everything runs smoothly. Only thing is that a column of pixels seem to be dead, but he's getting a replacement screen.
Anyway, he is truly amazed by the difference. I'm confident that it will last for at least another two years. It will eventually become slower, but actually I don't think it will be as bad as with the iPhone 4s. That thing was almost bricked and battery life sucked. The 5s suits all of his needs for the next couple of years.