I was a 4S owner, so no brainer there. But Apple proved me wrong. I had the opinion before the 5S came out that iphone 5 users had no business in upgrading to the 5S. Now I think I was so wrong. The fingerprint sensor is so good and the slow mo feature so cool that I think just those two features makes the upgrade from the 5 worth it.
I might agree with you if I didn't already own a GoPro that does slow mo, bro, so...that leaves just the fingerprint reader and the A7 64-bit processor.
I'm not saying I don't want the 5S. I just don't want it enough to pay AT&T a hefty early upgrade fee for the privilege of owning one. In just 11 short months, I'll be eligible to upgrade to the iPhone 6 (or whatever they call it), which will have all the cool features of the iPhone 5S, plus even more speed, likely a different case, and perhaps something else that we don't know about yet.
I went from the iPhone to the iPhone 3G, and since then I've upgraded every two years.
With the iPad, I've owned every generation except the 4th. When I got the iPad Air, I gave my third generation iPad to my sister, who gave her iPad 2 to my mother, who gave her first generation iPad (formerly mine) to my 1-year-old nephew.