My usual paddle partner and I have tripped with Kingfisher once. 

It hardly felt like tripping with someone I didn't know, though.  Considering we each have 1700+ posts on here and that we've met several times at Canoecopia, plus each of us has submitted trip reports on QJ, I felt like we each had a pretty good idea of what to expect out of the other.  I'd go so far as to say that there were less surprises out of that trip than trips I've taken with friends that I knew in person.

I would trip with KF again, along with quite a few others on this site.  I don't think we slowed down KF too much...   :D