Never really done much Word Processing on the Amiga. But as the topic keeps coming up on the forum and people does seem to think its an important aspect of computing. I would suggest LaTeX, I use LaTeX for writing text, posters and even to make presentations using the excellent Beamer package but on a *nix platform. I know people were using it on Amiga back in the days so I'm sure one can get it running now.
Found this on Aminet,
http://it.aminet.net/text/tex/Tex-Setup.readme
