I live down towards Lancaster and my reception has been good. My friends use their iPhones while working in Hershey and generally have a good experience. When I start exploring back roads in Lancaster and up towards Elizabethtown and whatnot, reception does fade between EDGE and 3G. Like most places, the closer you are to a populated area or a main highway, the better chance of having 3G.
If you travel anywhere north of Williamsport on a regular basis, AT&T has very few towers up that way.