I did that maybe six months ago. There are things I miss about my iPhone (my music mainly) but I do like a lot of things about my S4. I like the bigger screen and the capability to move icons to the back screen if I don't use them on a regular basis.
I know there are ways to put my music back on my phone but I haven't been brave enough to try it yet. Someday (and it isn't the end of the world because I still have my iPod).
Also, I do have a lot of iTunes cards yet and I've stopped buying music (thank you to the library) but like I said-I do still have the iPod and my Iphone as a back up and my kids have iTouches so....
All in all, I am surviving with the S4 and the bigger screen makes up for a lot of things.