I have rarely taken advantage of reciprocal links, simply because the most relevant candidates always seemed to be competitors. However, on a site I managed for a contracting company, I did exchange links with several other contractors, that were either complementary or non-competitive. All of us were well-known enough that we all benefited, in traffic and in sales. To me, relevancy was paramount. Then reputation. PR didn't really enter into it, although it perhaps should have. I wasn't culling that large a list of prospects, and all were personally known to me, so PR meant little.