There have quite a significant number of changes and improvements on the previous stable release (0.5.2) which are documented as follows in the release notes:
This latest release of Habari contains some major improvements and feature changes.
- ACL ( Access Control Lists ) support is introduced. With ACL, not only does Habari have support for users, group support has been added. Groups can be assigned specific rights that limit what parts of your site the groups members can access, ranging from only being able to read and comment on published posts ( anonymous users ) to being able to do anything on the site ( administrators ), and everything in between. This support is fully transparent to single-user sites, but can make life much easier for sites with multiple authors and user classes.
- There have been improvements to the admin interface.
- Sites that use SQLite as the storage database should see an increase in performance.
- UTF8 support has been improved. For previous users of Habari, part of the upgrade process is to ensure the database is utilizing UTF8 properly.
- Support for HiEngine, Habari's theme templating system, has been improved. Theme creators now have the option of creating good looking themes using either raw PHP calls, or HiEngine templating.
- Help support for plugins in the admin interface.
- Tag support is still built in, but the tag drawer has been moved to a plugin to improve the publish page performance for sites with hundreds of tags.
- The format of Habari's configuration file has changed. For those who have left it writable, the upgrade will be transparent. For those who have made it read only, it is recommended that it be made writable before upgrading, then set back to read only. If you don't wish to do this, see the upgrading instructions for details.
- The Serendipity importer is now hosted on the Habari Extras repository, and no longer ships with Habari. An importer for WordPress databases up through version 2.7.1 is included. The importer has had many improvements in this version.
- Habari now ships with a plugin that allows you to create private posts. With this plugin enabled, you can make a post available for reading to only a selected group of readers.
The release notes also touch on one potentially major loss of functionality, and that's the loss of PostgreSQL. Unfortunately, the demand and usage of PostgreSQL seems to have dwindled off so this part of the code hasn't been updated. If you're using PostgreSQL and are handy with PHP, please feel free to get porting and log a ticket with your changes.