SKAERTUS  Mellel is the best word processor in any platform. Very fast, very stable, very low on system resources. It has lots of well-designed features, especially the ones suited for academic writing. Its cross-references feature is miles ahead of Microsoft Word (Apple Pages not even supports it...). Styles are great too.

I've found its interface to be quite intuitive, and the tutorial is simple to check for information when you need it. It is not similar to Microsoft Word, and that is why users may complain a little. However, I didn't find any difficulty in exploring all of its features.

Mellel is compatible with .DOC and .RTF files, but not fully compatible, especially because Mellel implements its features in a way completely different from Word and other standard word processors. However, you may import and export from .RTF and .DOC and, while the layout may get screwed up, the text structure is maintained.

I've found Mellel to be the fastest and most streamlined of all MacOS word processors. Nisus Writer Pro is great too, but Mellel is even better. It's more and more becoming a killer app on the MacOS.  
(Version 2.6.1)