Mac

iTunes 10.4 is now designed for OS X Lion. You can now use iTunes with OS X Lion's new Full-Screen App capability, which allows you to use iTunes and other without distractions. Navigate between your full-screen apps with a simple gesture. 

iTunes is now a 64-bit Cocoa application on OS X Lion and includes a number of important stability and performance improvements. Some iTunes plug-ins may no longer be compatible with this version of iTunes. Please contact the plug-in developer for an updated plug-in compatible with iTunes 10.4.

Windows

iTunes 10.4 provides a number of important stability and performance improvements.