Dr. Drang has a solid case explaining why it’s a good idea to go independent with your word processing, i.e. rely on nothing but plain text files:

In fact, the one constant in the history of word processors is their insistence on changing file formats. It’s the reason I quit using word processors over 15 years ago. I recognize that Adam, being a publisher and needing to work with several authors, doesn’t have the freedom I have, but as long as his workflow includes a word processor, he’s going to run into frustrations like this.