Apple just released an update for iTunes, which reaches version 10.4 and adds a number of important improvements in OS X Lion. The new iTunes does in fact support full-screen mode, but more importantly is a full 64-bit Cocoa application on OS X Lion. This should enable for speedier performances and a more stable app, though we haven’t been able to test it just yet. iTunes 10.4 comes ahead of iTunes 10.5, which has already been seeded to developers and will likely debut this Fall alongside iOS 5 and iCloud. The new iCloud-based features such as automatic downloads and iTunes in the Cloud, however, are available to iTunes 10.3, and now iTunes 10.4, users as well, without needing to get the developer preview.

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.

To enjoy the latest Cocoa enhancements and 64-bit support, you’ll need to have Lion installed on your machine. You can download iTunes 10.4 from Apple’s site or Software Update now.

Update: As far as performances go, if iTunes 10.5 beta is of any indication on my late-2008 MacBook Pro with SSD, the application does seem a little snappier and generally more responsive than older iTunes versions, though it’s not an immediately visible change. The trained eyes of developers will notice the performance improvements and technical changes, but to the average user it’s just the same iTunes, only slightly faster.