“New for 1.92: Playability status with the PS3 system has changed for some PlayStation 2 format titles. To check on the latest status, visit the search site for compatible titles (coming soon).”
The update page says little beyond that. If you aren't using your PS3 to play older games, there is probably no reason to upgrade. It only apples to units sold in North America, so Japan, European and other markets cannot use this update... yet.