Nisus Writer Pro 2.0
This major upgrade for Nisus Writer Pro adds change tracking, drawing tools, PDFs with clickable links and tables of contents (which Microsoft Word and Pages still can’t do, as far as I know), EPUB export, and lots more.
Update (2011-06-09): Joe “Nisus Way” Kissell reviews Nisus Writer Pro 2.0:
After following Nisus Writer’s ups and downs carefully these many years, I am equally shocked and delighted to say this is the first version of the application since Mac OS X was released — over ten years ago — that I can seriously contemplate using for my own professional writing.