The FS change notification processing has been rewritten and now uses same back-end on Windows and Mac. The Mac version now uses the official file system notification API introduced in Mac OS X 10.5, so you no longer need to enter your root password to enable notifications processing. On Mac OS X 10.4, file system change notifications are no longer supported.
Most of the functionality of the SmartIntroduce plugin has been reimplemented as IDEA core features. Actions like Introduce Variable, Introduce Constant and Introduce Parameter are now more flexible in determining the value from which the new variable will be introduced.
IDEA can now highlight usages of the identifier under caret as you move through the source code. This is currently off by default, and can be enabled in Settings | Editor | Behavior | Highlight usages of element at caret.
The standard VCS actions (commit, update, revert, diff and history) have been added to the main toolbar.
Assorted performance improvements (more lazy initialization of components, background preloading of actions, asynchronous update of icons, faster completion, etc.)
Creating a module from a Maven archetype is now supported.