What's New in Plone 2.5

A summary of what's new in Plone 2.5.

Plone 2.5 is a release with a significant focus on improved infrastructure. This is the first release of Plone that utilizes Zope 3 technologies, and it is an important step in transitioning Plone to use these components throughout the system.  Though there are a few user-visible changes in this release, the bulk of the changes are under the hood and will ultimately have a strong influence on future Plone development.

Notable features in Plone 2.5 are:


Extensive use of Zope 3 technologies throughout
Zope 3 views are now used to generate the standard portlets and other navigation elements.  Many frequently used python scripts have been replaced with Zope 3 view methods.  Additionally, the navigation related methods which were previously difficult to customize, can now be customized using zcml to provide alternate adapters and/or views.  The end result is increased performance, and in some increased flexibility, customizability, and testability.  As plone evolves it will continue to take advantage of more and more of the technologies offered by Zope 3.
Improved internationalization infrastructure
Plone now uses Zope 3 MessageIDs throughout, which makes it possible to cleanly provide translated strings from python code to the browser.  It is now easier than ever for product developers to create internationalized applications.
Pluggable Authentication Service
The new authentication structure in Plone 2.5 makes it very easy to integrate any kind of authentication with Plone.  Roles, groups, authentication, and user data are all managed with separate plugins, and each can potentially get its data from a different source.  This offers integrators substantial flexibility.  Plugins for LDAP and GMail (!) already exist, and more are easily added.
Support for XML exports of site configurations
It is now easy to replicate a particular site configuration across multiple instances, making it easy to create setup policies for sites.  This product has become the standard for Site creation/configuration and product customization in CMF, and is now an integral part of Plone.
Resource compression
A new version of ResourceRegistries is included which features compression of css and js files.  These files previously constituted more than 80% of each page downloaded, resulting in slow page renders and heavy bandwidth usage.  The compression reduces the size of these files by about 25% out-of-the-box, and up to 50% when maximum compression is enabled.
New caching infrastructure
The CacheFu project now ships with Plone, and after setup leads to between 10x to 40x faster page loads of the view templates, depending on setup — and makes caching transparent to the end-user.
Placeful Workflow
It is now possible to have workflow policies determined by location in the portal, not just by item type.  This means that different parts of the portal can have different security settings, and entirely different workflow paths for the same types of objects.
Status message updates
A new infrastructure for displaying status messages means that for the first time these messages can be translated along with the rest of the Plone interface.  As an added benefit, when products use the new status message techniques there are no longer unattractive query strings in the resultant URLs. 
Drag and Drop reordering of folder contents
The folder contents view now supports AJAX-based drag and drop reordering of objects in a folder.  This makes it much easier to reordering many objects, and it's fun to play with too. 
Easier recovery from catalog related issues
Plone includes a new mechanism for fully rebuilding the portal_catalog from scratch.  Site admins have been known to occasionally create inconsistencies in their site catalog.  In prior releases the mechanisms for repairing the catalog were laborious and error prone, now it can be done correctly and repeatably with a single button press.
Support for the latest technologies
Zope 2.9 and Python 2.4 are now supported by default.

For more detail, have a look at the included change log, and read the full release notes.