I took the plunge and created a PBWiki site for the co-authored writing project. (It's private. Password protected. No, I'm not sharing the url! LOL)
I've been playing with the software, trying to figure it out. There is a bit of a learning curve, but it definitely feels like something that you need to just jump into the sandbox and play with. Setting up pages, deleting pages, linking to pages, formatting text correctly, uploading pictures and files.
Not sure my co-writers will have the patience for learning it -- not when their energy could be used for writing. (Note to self...)
Grace did post something to the site. She's the one who's done the bulk of the work so far.
I think Destiny is too busy at her day job to have even seen my email to her about it yet.
I still believe the site will be best utilized by us for sharing background material, and keeping track of that background material when we go to write future projects in the same universe. (Oh, we will!)
Don't plan to ever make the site public, though. Not when the intention is to get the work published in a traditional format.
See A place to collaborate below for more information.