Andrew has now committed a very spiffy improvement to the little-known full screen editing mode in WordPress.

The Distraction Free Writing mode has been in trunk since yesterday. Would appreciate comments, suggestions, opinions, etc. Bug reports should probably go on #17136.

Via WordPress Development Updates

Here are some screenshots, for your viewing pleasure, of what is currently in WP trunk.

Activate full-screen mode from the editor toolbar.

Nothing but you and your ideas. Full focus FTW!

Provides a clean, minimal toolbar on mouse movement.

Works with the standard admin features, like links and media.