I mostly use Google Docs but, frankly, for my writing just about anything works. (Being able to work in shared docs is useful but not much else matters.) I'll use Scrivener to do the first pass at assembling a book but, other than that, anything that lets me put sentences down on a page and edit them is fine.

I used to use Word and I'll sometimes use it if I need to if that's what a publisher is using but I never really loved the ribbon and there's way too much clutter that I never use.