Good for
- note taking
- journaling
- writing & composition
- task/project management
- rapid prototyping development
- lists within lists; zoom in and out
- multiple node types: todo items, embedded images, code snippets, etc.
- you own your data -- keep it local, sync to github gist, google drive, etc
- multi-pane interface (arbitrary splitting)
- web repl -- connect to a javascript kernel, ipython, clojure, etc.
- extensible
- Workflowy
- Evernote
- Trello
- Whiteboards
- GinkoApp
It is in alpha stages right now. Many things are wonderful and I use it every day, but some core things might change slightly in the near future.