This may be the biggest upgrade to WordPress since the jump from 1.5 to 2.0. There are numerous changes on the front-end and the back-end. The admin panel has probably seen the most radical changes, as it has been completely redesigned from the ground up. And they redesigned wordpress.org to boot! So that’s why it took 6 months for v2.5 to come out…

A quick round up of the new features:

• Multi-File Uploading
• Upgrade Plugins with a single click
• Photo Galleries
• A Dashboard you can Customize
• Salted Passwords and Encrypted Cookies to increase the security of the project
• A Media Library of all your uploaded assets
• A WYSIWYG that doesn’t mess up your code (zomg!)
• Protection against Concurrent Post Editing
• Writing in Full Screen Mode
• And a search engine that covers both posts AND pages (long the domain of a plugin)

You can read all about it in the official announcement.