This is a Content Management System built on Python & itools, among other features ikaaro provides:
- content and document management (index&search, metadata, etc.) - multilingual user interfaces and content - high level modules: wiki, forum, tracker, etc.
This release has seen the major changes in the user interface for a long time. Most notably the backoffice is now integrated into the frontoffice. When the user logs in the application, the backoffice interfaces appear.
A number of changes have been made to satisfy this new approach. In particular the backoffice interfaces are lighter. For instance the two level drop down menu has been replaced by a discrete flat menu. Another example, now the right column, instead of being always visible, contains context menus that appear or dissappear depending on the resource & view being displayed.
The internationalization and localization of the user interfaces has also been considerably improved. For example now there is a global language selector, available in both the front and back office modes. And several components are multilingual now, like the HTML editor (TinyMCE ) and the tracker tables.
Some other features have been added to the issue tracker. First, a calendar has been integrated, in order to track resources attached to an issue. Another important change, there is a new field called 'Products', and now modules and versions are classified by product (inspiration from bugzilla ).
Many other changes have been made to the user interface, too many to enumerate them here.
The application behaviour is also more respectful of the REST  paradigm. For instance now there are much less redirections than before.
However, it is probably the changes under the hood that are most important. Specifically the architecture changes concerning the way a resource view is built. Before a view was a resource method, simple enough but not very scalable. Now a view is a class in itself, what enhances the possibilities of code refactoring.
Again, the changes to the programming interface are too many to enumerate here. See the upgrade notes for more.
Bug Tracker http://bugs.hforge.org/