Wiki markup can be made easier with javascript widgets similar to wikipedia. That's not a big deal.
The ease of editing, managing, and linking pages is why I prefer a wiki for documentation. The learning curve is very shallow for a wiki. The interface for a usual CMS is much more complicated.
XCMS was built for a client, and after that job, I contributed the code, hoping someone could continue work on it if they needed it. I unfortunately haven't had time for it. I think the user interface is barely usable for a CMS,a nd for managing documentation, its just wrong.
I like the ability to link to any page more than a hierarchy of documentation. If you want to replicate a book in computer form a hierarchy can work well, but I think HTML and the web offer a better way of using documentation.
