We're a self-funded, boot-strapping startup, so conserving cash is pretty important to us. I could pay to use a co-working space, but the value just doesn't seem to be there for me. When I want to be around other people, I go work at the cafe at Barnes & Noble near my apartment, or at SplatSpace (hackerspace in Durham), or Beyu Cafe (a popular restaurant in Durham, which is popular with the startup set here), or something of that nature.

When co-working space would be valuable to me, would be when we start needing a private space for meetings (ie, a conference room) on a relatively frequent basis. And even then, I'm not sure we couldn't come up with a better arrangement. Depends on how much the local co-working place is charging and what kinds of models/plans they have in place.