The iTunes 12.4 update appears to have improved the speed of Apple's jukebox software, even though the company isn't actively promoting that fact, according to user comments on Reddit and Twitter, and first-hand experience by AppleInsider.
On OS X at least, the app is performing better not just in terms of general navigation but in several other respects, such as load times. One Reddit user commented that whereas it previously took about three minutes for iTunes to check the library on their 2012 MacBook Pro, the 12.4 update reduced that time to 20 seconds.
The main beneficiaries of Apple's speed boosts appear to be Mac owners, as a number of Windows users have suggested the software is largely the same on their platform. One AppleInsider editor did encounter slightly snappier Windows performance.
iTunes has often been attacked as a sluggish and cumbersome app, particularly on Windows. The issue has become more serious over the years, since Apple has attached a growing number of non-music functions like video, app downloads, e-books, and most recently Apple Music. iPhone, iPad, and iPod owners are often dependent on the software for sync and backup.
Officially the main purpose of the 12.4 update was a redesigned interface, for instance restoring the sidebar as a key component, and adding Forward and Back buttons to make it easier to backtrack.