As I'm in the middle of setting up a XenCarta wiki, thought I'd post some thoughts. Just my experience so far, and my $0.02.
I'm in the process of migrating my site, a site much like this one, which sells and supports a technical product, with several thousand active users at any one time. We've completed the CMS and forum steps of the migration, from Joomla! 1.5 and vBulletin 3.7 to J! 2.5 and XenForo. We use jFusion to control single sign on, with J! as the 'master', using a combo jFusion plugin / XenForo addon which I've taken over ownership of, after the author had to move on.
We also run MediaWiki, which technically has the ability to also have single sign on with J!, but we had so many issues with that, we turned it off. I really am not a big fan of MediaWiki. For what we need, which is very narrowly focused on being a technical wiki for our product, MediaWiki is overkill, and IMHO is hard to 'drive', as even with the rich editing, still requires knowledge of Markdown and Wiki structure. To be frank, I hate wiki editing.
Having a separate Wiki system is problematic in other ways. The key being "separate". There's absolute zero level of integration between it, and where we (us and our clients) live, in the forums / CMS. So having a WiKi which integrates with these, especially in the forums, where references to the Wiki are the most important, could be Godsend.
I'm currently playing with XenCarta. Which looks to have pretty much everything I need in a wiki, and has excellent tight integration with the forums. I particularly like that the discussions exist as threads in designated forums, and that the XC wiki content is included in a global search. It's structurally restrictive, with a simple "each page has a single parent" (one to many) approach, so there's just a single 'pages' table, rather than a "real" wiki's pages, pagelinks, revisions 'many to many' structure. But for what I need, that's fine.
I'm in the middle of importing my MediaWiki content, about 250 pages, in to XenCarta. It won't be a trivial task, but I've already got all the basic content in to XC, by creating a MySQL view of the MediaWiki tables, inner joining the latest revision for each page, that creates the structure the XC tables page uses. I then export that view as CSV, and import it into my XC 'pages' table.
The problematic part of this stage is establishing the tree structure, as there really is no way interpret the MW link relationships to establish which page is "the" (singular) parent of another, as MW uses a 'many to many' relationship for page links. So it looks like I'll have to do a lot of manual restructuring in XC, resetting the 'parent page' for most of the content.
The other issue is of course Markdown. There doesn't seem to be a Markdown to BBCode converter, so I'll need to create something to do that, to at least convert basic formatting, image links, and content links. Which isn't trivial, as it involves a lot of work processing the MW tables to extract actual links from Markup.
The advantages I see of having the wiki full integrated with the forums are tremendous. Just having the wiki included in a forum search will be a massive win, and save us a huge amount of answering questions with a pointer to a wiki page. I think it will also greatly increase the amount of user input in the wiki. I know even I find it a chore to add content to MediaWiki, and would do it a lot more often if it was as routine as posting a thread on the forum. Just these two things combined would make a massive difference.
The only down side I see is having our data in a 'proprietary' format, used only by one addon on one forum system. To me, that's not such a huge issue, as I'm familiar enough with MySQL to import that into something else, if we ever migrated to something else. But I think for any XF based wiki, an import/export with standard MediaWiki would be essential.
Anyway, that's where I'm at ...
-- hugh
