Major new release this morning!
Better clustering. We've switched to a new clustering algorithm that produces much more intelligible output. If you didn't quite love the way Overview was organizing your documents before, please try again now.
Sharable document sets. A little checkbox next to each of your document set allows you to share it with all users (specific user sharing coming soon.)

You can import a shared document set through the new import dialog. Note that currently this clones the document set, meaning that any changes to the clone will not be reflected in the original, and vice-versa.

The importer of the shared document set must still have permission, through DocumentCloud, to access any private documents.
Integrated Tweet display. It's possible (and fun!) to use Overview to organize and explore a large volume of tweets. To do this, you will need to capture your tweets to a CSV file and upload it to Overview, as explained
here. The tweet text should be in the text column, and to use the integrated viewer the URL of the original tweet should be in the URL column, e.g.
https://twitter.com/jonathanstray/status/302145598306516992.
Then you will see Tweets nicely displayed in native format right within Overview, including attached links, conversations, etc.:

Keyboard shortcuts: For super-fast navigation through your documents, use this:
Arrow keys - navigate through the nodes of the tree
j - next document in list
k - previous document in list
MOAR DOCUMENTS! The limit is now 20k. If you try to import a document set with more than this, Overview will import only the first 20,000/
Thanks all, and happy document mining!
- Jonathan