As a student, I frequently ask friends to read and edit my work. There are a few ways to go about doing this.
I can print a hardcopy and hand this to a friend. I have to find a printer, kill a tree, make paper, find a friend, deliver paper, etc. This is obviously not the right answer.
I can email a friend a version via email, have them save it, edit it, then save it again, then send it back. This requires a lot of unnecessary saving and sending.
Google docs does a nice job of allowing people to edit a document live, but problems still exist. First, I don't want people making changes without my approval. But I do want the ability to easily make a suggested change. Word's attempt to solve this problem (track changes), does not meet my expectations. Draft (Draftin.com) does.
After just playing with it a bit, I plan to use it whenever I need editing help from friends. Friends can edit papers and provide me with feedback. I can accept or deny this feedback with the click of a button. If I need another set of eyes, I can use the "ask a pro" feature. This is the best tool I have found for editing.
I also think it's a pretty rad tool for creating. It incorporates automatic saving, the ability to easily view drafts and a clean UI. It provides the ability to view documents on any computer or device, just like dropbox (oh and it can sync docs with Dropbox and Evernote).
I'm not sure this will replace word for everything right away. But it will certainly be my go-to for things requiring a second set of eyes.