I'm a longtime Apple fan and actually work for a company as a Mac rep (computers, iPads, and iPods only - no phones). I've had an iPhone since the 3gs version came out. My most recent iPhone was a 4s, and when it came time for my upgrade, I checked to see if there were any rumors that Apple was planning on a bigger screen. I found the screen to be too small for my aging eyes, so made the leap to the S4 a few weeks ago. If Apple ever does make a bigger phone, I might go back as I miss the ability to sync my phone so simply with my other Apple devices. With that being said, there are two key features that I just love about the S4 - 1. the ability to call via wifi. I love that as soon as I walk in the door at home or work, wifi calling kicks in with no intervention by me. I have, however, discovered a bug - when going from wifi to cellular, I have to reboot the phone, otherwise I frequently cannot sent or receive calls. 2. I love the fact that the app icon gives you a list of app in alphabetical order! Much better than scrolling through page after page, or going to the "search" screen to locate an app.
There is a bit of a learning curve, but so far I'm satisfied!