I'm experiencing something similar regarding the vertical lines on the screen.
I had a 5 before my new 5S, so I'm able to compare them side-by-side.
It's barely, barely, and I mean BARELY noticeable. I tried taking pictures to upload here, but it's so barely noticeable that you really can't even see it in the pictures.
However, at least to me, I can clearly see extremely thin vertical lines running down the length of the screen on the 5S. Where the 5 looked like one uniform image, the 5S appears a little bit more like a regular, non-retina screen, in that it seems like the pixels are visible - at least vertically.
I'm hesitant to go to a genius to see what's up, because I think they're going to look at me like I'm crazy. I have very good eyesight, and I doubt most other people would notice a difference at all.
But, if more people post on here saying that they're seeing something similar, that might change my mind.