Scrivener

I completed a PhD using older versions of Scrivener, using it every day for 5 years. It is an incredible tool for writing, especially for longer pieces where structure is difficult and important.

Being able to see the overall flow of a piece both in the 'binder' list and in cork board/card format was invaluable. Scrivener's thoughtful and sophisticated UI freed me to write more fluently as and when ideas came, without being distracted by second order thoughts about how to piece the ideas together. I knew I would be able to move what I had written around within the structure of a larger piece very easily and effectively later on.

I rewrote and restructured a number of chapters, and indeed the whole structure of the thesis, many times. Again the cork board, binder and 'snapshot' tools made the work of keeping track of changes and movements an absolute pleasure.

The screen set up with binder on the left, the actual text you're working on in the middle, and the 'inspector' with comments, footnotes and snapshots on the right hand side of the screen is FAR superior to what you get with more basic word processing tools, because it allows you to see and edit footnotes, comments, and the entire structure of your piece while you are working. No more annoying scrolling and hovering with the mouse.

The newest version seems to have a few nice little improvements, the most notable of which appears to be the improvement in interoperability of 'styles' with other word processors.

I can't recommend Scrivener highly enough for anyone who is serious about writing.