I have a bias against wikis of all kinds. If left to their own devices, they tend to become an unstructured mess. Of course, the lack of structure is what makes them useful for what Wes is proposing: gathering knowledge and organizing it as it evolves. But someone will need to play the “librarian” role to keep it in shape.
I would advocate keeping bug/feature reports in JIRA, and user doc where it is now, and only use wiki for the small amount that doesn’t fit into that.