Once upon a time, I decided I'd rather have copious documentation rather than beautiful documentation, and used Word for the project. It's just so much easier to create and edit, esp. if inserting illustrations and such.

So maybe you should investigate tilly's hint on LyX further. With LyX you get some WYSIWYG and the power of LaTeX. Together with Ghostscript (ps2pdf), pdfTeX, html2latex, latex2html and latex2rtf you will get a powerfull typsetting environment which isn't that difficult to learn.
But it is still TeX, meaning a typsetting language. I would rather use XML or some other logical markup and then convert it to LaTeX or whatever for typsetting on paper, as pdf or to produce rtf documents.

Hanamaki