For heavy duty stuff, I use Mellel; never crashed in 7+ years of use, especially good at long documents, and handles Hebrew properly within an English context. Very powerful auto-titles, multiple independent notestreams, superb styles sheets.
I also use Nisus Writer Pro, very capable program, but more for short, quick projects.
Both work well with Bookends and Sente.
If writing is your thing and you only need to export to .rtf, then consider Scrivener. Superb planning, research, integration tool, best all in one writing tool.
And if you want real power, consider Tinderbox for research, Scrivener for writing tool (buy as a bundle and save). Tinderbox will expand to meet your level no matter how advanced you go.