The update also finally provides iTunes with 64-bit support, a change that won’t have obvious short-term impact but is necessary for the software’s future development. Cupertino’s developers state that this improvement results in better performance and stability. However, the switch to 64-bit could potentially break some iTunes plugins until they are updated.
iWork has received an update to version 6, which provides the software with support for Lion’s new functionality. Resume, Auto Save, and Version features are now a part of Pages, Numbers and Keynote, making it easier for users to switch between documents and recover them should a crash or other error occur.
You’ll need Lion OS X to receive the full benefit of iTunes 10.4, but the software is compatible with Mac OS X 10.5 or better. The update to iWork version 6 requires Mac OS X 10.6.6 or better, but most of the new features will not work without Lion.
Source: Apple Insider