* the ability to expand and collapse tabbed lists subordinate to another heading, hiding or revealing them. That makes it much easier to stay on top of the structure of a document.
* the ability to effortlessly drag around (or use keyboard shortcuts to move) those structured paragraphs, thereby effecting major structural revisions rapidly.
What's interesting about Little Outliner (from Dave Winer, the man who gave us a lot of the late, great outliners in the 1990s, and invented the RSS feed) is that although an outline is created within a browser, it is saved locally.
Each approach - local storage and cloud storage - has its advantages. One is personal and private. The other enables both ubiquity (access from multiple locations and devices), and collaboration.
But on the whole, I like seeing outliners back in the news. Winer says he's looking to enhance the product rapidly, and networking outlines seems inevitable.