I have written several novels in Xy4, and created hundreds of complex indexes (biographies, history books, etc.). I basically live in XyWrite 4. I switched over from Xy3+ with a little help from this list (thank you Carl!). The transition guide in the Xy4 manuals was especially helpful, as was using the Xy4-3 Keyboard file (instead of the standard XY4.KBD). I rarely use the menus, but when I need them they come in handy. I had to change a few defaults to duplicate some Xy3 settings I'd become used to, but after that the transition was pretty easy.
What I love about Xy4 (these capabilities may be same as Xy3, but it's been many years since I used that program)
-The ability to create small macros to speed my work and create my own keyboard file incorporating those macros.
-wildcard search and replace
-sheer speed, especially to sort very long files (such as all those indexes).
-The Xy4 manuals and customization guide
I could write novels in Word, but I couldn't use it to create the detailed indexes I do for publishers. Any complex text manipulation is a million times easier in Xy than in any other word processor I have tried. When I have to seriously rewrite or revise prose, I always do it in Xy4.
And don't get me started on dedicated indexing programs.