[Reposted from c3o]
If you want to edit documents, I’ve read that Abiword also has Collab plugin, though I never tried it.
What I liked of Gobby is, that it is multiplatform, I don’t like being tied to mac platform, although I use it. Collaboration especially should not force all users to use the same platform. Anyways, as I think of it, there are probably better solutions based on whether you want to edit source code or documents.