For serious technical documentation, I use DocBook, an XML/SGML DTD designed for techincal documents. I would also look at LaTex and variations thereon. A lot of large companies like IBM and HP use SGML, as does the U.S. Air Force and other government agencies, for technical documentation.
To add to this. Many of our scientists use LaTex for technical papers. The Windows users were so frustrated with trying to get things formatted in Word and the LaTex users were not having problems.
There was a review of OOo 2.0 preRelease that I read today and it was quited good.
http://www.theinquirer.net/?article=20293
-- Robin Laing
