The settings app has been rebuilt from the ground up to hopefully offer better control over your device. New adaptive icons will help Android retain a similar look regardless of which OEM you're using. Wide-gamut color support offers improved graphics on high-end devices. Wi-Fi Aware will allow for direct Wi-Fi transfers without an Internet connection. Better WebView will offer enhanced security for web-browsing. And finally, my favorite - autofill APIs so you can quickly fill in saved passwords from password managing applications.
That's in addition to the slew of improvements we already know about, and there's always the possibility that Google will reveal even more at their annual I/O event in May.