Testing the incredibly good text editor WriteBox, it's a Chrome App and will replace ByWordfor me on my Mac. As you can see in this video, it has a non distracting environment. I like that a lot, and it supports both Google Drive and DropBox.
WriteBox doesn't support MarkDown as ByWord for Mac does though, but I don't need MarkDown all the time when writing, for example when writing video description text, orGoogle+ posts. And I have a Chrome App for that too, but that is another video ;)
This is one more step in my Google experience where I am trying to use my MacBook Air as a "ChromeBook", by only using Chrome and Chrome Apps. And still having the MacBook Air and OS X as a "backup" when needed. For example when doing more advanced stuff like Video Editing, recording screencasts and more.
That makes my MacBook Air a "Super ChromeBook", and that is what I think Google is doing with Chrome at the moment. Making "Chrome OS" available on any computer as a layer above your real OS. That is the future for cloud computing and Chrome OS.