All modern mobile devices use Flash storage as their main form of memory. While Flash storage is significantly faster than traditional hard-drive disks, it isn’t invulnerable to slowing down over time.
There have, however, been technologies and strategies developed to combat this. TRIM, which is supported on both Windows and OS X with most SSDs, is one of these technologies, and Android 4.3 includes it. Does it matter, though?
Google’s original Nexus 7 was released last year to quite a bit of fanfare: the device was fast and smooth, and had lots of potential. However, the device became significantly slower as time went on. That was the result of garbage building up on the Flash memory, causing the system to slow down. Apparently, Android 4.3 and TRIM support fixes that issue, making the original Nexus 7 as fast as it once was.
Regardless of if you will notice a major difference once Android 4.3 is installed, it’s excellent that this technology is now built-in to Android.