[b14ck]

To me, wikis just seem 'lazy'. Projects that use wikis as a primary form of documentation make users feel like the project is un-cared for, and not worth documenting.

I have absolutely no stats to back this up--but having officially written documentation gives projects a really good 'feel', and makes it a lot simpler for users to get started (IMO).

[andrewflnr]

That seems strange to me. It's possible to do a really nice job with it, as evidenced by (at least) the Blueprints project: https://github.com/tinkerpop/blueprints/wiki