Not really, it's the concept that draws me in, not the RP'ers. In fact, I prefer to RP with new people when possible in order to keep things fresh. Case in point, I was part of a PnP group and we ran various campaigns using different systems (D&D 4th & 5th Ed, Savage Worlds, Edge of the Empire, etc) over a period of 6 years. These were some exceptional RP'ers, but we eventually reached a point where it was pretty predictable. Sure, we made new and different characters every time, but I knew the people themselves so well that I had a pretty good idea of what was going to go down in the RP beforehand.
That's a pretty extreme example, I agree, but I've fallen into the same trap in forum RP as well. It's always great fun to write with trusted people, but you just grow too comfortable after a while, know what I'm saying?