This release focuses on three major changes/features:
Rewritten using the FOF framework. Admin Tools was rewritten to make use of Akeeba Framework-on-Framework (FOF), a programming library built on top of the trusted and tested Joomla! Framework. Already used by Akeeba Subscriptions, this library allows us to deliver more robust software, while making adaptations to future versions of Joomla! much easier.
Joomla! 2.5 ready. This version of Admin Tools can run on the upcoming Joomla! 2.5 long-term support release. Please review the last section of this release announcement for more information.
PHP File Change Scanner (Professional release only). A major new addition to Admin Tools, this feature allows you to monitor your site for modified or added PHP files, which could indicate a hacked site. Moreover, it allows you to perform a preliminary, automated security audit of your PHP files, detecting suspicious files. This information can be invaluable when trying to fix a hacked site, as it will narrow down the list of PHP files you have to review by a factor of 20. Please make sure you read the documentation carefully before using this feature.