Google just announced a new Dart Editor version. You can get if from here:
http://gsdview.appspot.com/dart-editor-archive-integration/latest/
These are the improvements:
- Moved bundled libraries out of plugins into new “libraries” directory
- Indexer improvements including integration into builder
- Editor tab tooltip shows path of the files being edited
- Problems view sorting fixes
- New File wizard to opens created file in the default editor for that file type, instead of the plain text editor
- DartC improvements
From my point of view this is just a minor enhancement release. Still there is some stuff which is required to make the Editor good for all-day-work. For example: deleting files or creating folders 
Anyway, it is worth to look at it if you would like to learn this language, because you get a code completion and do not need to build Dart yourself. Get it, while it is hot! If in doubt, take a look at the tutorial.