Plain text is great. There's so much you can do with it that you can't in word or even latex. I'll write all my coursework assignments in sublime with a double column layout so I can have my notes in one window and my draft in the other. I can then check it all into my git server, run stats against my writing, and see more text without the need for scrolling. I can also search the entirety of my coursework or work notes much faster which is great to find all the references I made to a specific author. I still often have to copy text into word or latex formats but if you have the templating and styles set up that can be pretty quick work. It's nice having the raw text and formatted work seperate.
I've been writing a book for many years and my set up has always been this: Sublime text with 2 columns: notes on the right, text on the left.
When I write notes, or a blog post, or an essay, etc... I use Sublime and markdown. I can easily convert that to LaTeX with pandoc. For more complex rapport I have a script that do the translation from several .md files to one .tex file.
If I write a technical paper I just use LaTeX.
I will only use word for a quick and dirty rapport.
