Nisus 2.6 and larger is most excellent for entering and editing text. This version seems to keep up the improvements. While its features are not yet equivalent to classic Nisus, Nisus Writer Express is now worth using on OS X and I have started using it again after several years of false starts.

Especially useful are the non-contiguous selection, easy to use regular expressions for find/replace, on-the-fly word count, very easy to use keyboard mapping, the thesaurus and multiple clipboads---all good features for a professional writer.

I do almost all of my print and web publishing using the tools of TeX (see http://www.tug.org/mactex/) so I really don't care about Nisus styles, tables of content (can Nisus do one?) tables, footnotes, endnotes, headers/footers and the like. But it appears Nisus does these very well (I know how to use them, I just don't). You can even mix footnotes and endnotes in the same document, which could be useful when doing specialized publishing of educational documents (footnotes on the page and discussion questions in the endnotes), for example.

My son uses Nisus at college and transfers files back and forth with that nasty word processor developed by Microsoft. So Nisus apparently does this well, too. It certainly preserves much of the formating when opening Word text docs, but sometimes skips graphics. The file exchange is good enough for collaborative work on text docs, but probably not good enough for sharing docs with lots of images. I would just use Nisus and dump Word, but that is not always realistic.

So, if you need a great text processor with the features already mentioned, plus more, you might want to give the 30-day trial a look. The price is great and you can get a family license for $40 more.