The interface is minimal, when it's windowed there are no buttons or toolbars, so it doesn't distract from work. When it's in fullscreen, there's just text, no interface at all.
Write! uses a file format that saves all versions of a document. Meaning even if the app is closed and then opened up again, Write! can restore any previous version of the document.
Picks up where you left off next time you start the app
Write! saves the state that it's in when closed and restores that state when opened. You can pick up working on documents in the exact same place you left off - same documents open, same cursor placement, etc.