Based on my own personal experience:
Writing a book or serious letters:
1. Final Writer 97 (better Thesaurus)
2. Wordsworth AGA (better user interface)
3. LaTeX (You neeed to be dead serious with this one)
4. PageStream (Light, ez, fluffy) I couldn't live without it.
Writing Code:
GoldEd / Cubic IDE (It supports folding and unfolding & syntax hilighting so it blows away Cygus ED.
Cygnus ED. I still use this because it is what I learned on. Bad habits are hard to get rid of

((((((((((
Other's I would love to try beuase I keep heaaring goood things about them:
FrexxEd
TurboText
Black's Editor
Annotate
Idea Processor
Can anyone recommend me a code editor that works in full screen mode AND supports folding / unfolding) AND supports syntax hlighting/unhililithing? Preferably with example screenshots?