The update also brings Boost Mode to the PS4 Pro which can improve the performance of legacy titles that have not been have not been patched to take advantage of the PS4 Pro's faster CPU and its faster and double-sized GPU. This can provide a noticeable frame rate boost to some games with variable frame rates, and can provide frame rate stability for games that are programmed to run at 30 Hz or 60 Hz.
Boost Mode can also result in shorter load times, but it is not guaranteed to work on all games. You can enable it in Settings, under System.
Other improvements include GIF support, custom wallpaper, voice chat for Remote Play, improvements to resolution under PS VR and more.
Below is a video detailing the update.