Following up on Dee Elling's comment, here's a simple technical doc we created in the Confluence wiki (the PDF creation is a one button operation):

http://edocs.bea.com/alsb/docs26/pdf/aldsp_transport_for_alsb2_6.pdf

Although it would probably have been easier to create this in Framemaker, there are a lot of advantages to using a wiki, especially when it comes time for changes to be made in the document.

My personal opinion as to whether a wiki can scale to more major documentation challenges, it would seem that if a wiki can scale to contain an exponentially growing cohesive rendition of all the world's knowledge, it probably can handle a hardware or software doc set. Or, to put the shoe on the other foot, when will an XML editor and specialized CMS be required in order to keep wikipedia from becoming hopelessly confused (or confusing)?

The real challenge is creating a good hierarchy of information which would replace the book paradigm. While metadata to facilitate specialized searches would be nice, in reality (again, my opinion) 97% of users will be happy with what Google brings back from introspecting popular pages and xrefs.