I had been warned about the rocky stretch of the AT in Pennsylvania before the hike. The rocks themselves are nothing new; I have complained about walking over patches of rock since I started. The thing about PA's rocks is that they never take a break.
From about Duncannon, PA to High Point, NJ is a ridge line consisting of nothing but rubble. There is the occasional dirt road, but for most of the 200 miles you are carefully navigating rocky terrain. It's like playing Tetris with your feet. You constantly rotate your feet to fit in the spaces between the rocks as they come at you. Sometimes there is no space, forcing you to step on the sharp edges or steep angles. Averaging 2mph for the day is a challenge, even though you are not scaling any mountains. There are also huge boulder fields where you hop from rock to rock, hoping you don't slip off over the side (I actually enjoy the boulder fields). At the end of the day your feet hate you.
PA (and NJ) does try it's best to make up for the rocks, heat, and lack of water. Trail-angels are everywhere (especially the Billville crew) offering food, water, rides, and encouragement to help you get through this tough section. There are also many towns and places to get tap water. I think I got stream/spring water only once, and only ate a few meals out of my pack.
I saw many hikers skip huge sections of the trail here or even the entire state. It may not be the best part of the trail, but it is worth hiking through at least some of it. There are actually some good views to be found.
When I passed High Point in New Jersey, we finally got off this ridgeline. I don't expect the rocks to go away but hopefully they won't be quite as bad.