Improved camera app: The Google Play Edition HTC One and Samsung Galaxy S4 both include a new camera app, with controls that are closer to the bottom of the screen instead of dead-center in the focus area. It's a minor tweak, but one that should help people who snap photos with just one hand. The photo editor includes some new filters as well. It's no surprise that this improved camera app is on the way to Android 4.3.
Notification mystery features: Another bit of detective work by Android Police turned up signs of new notification features in Android 4.3. You might be able to view your entire notification history from within third-party apps, or you could potentially customize the notification bar in the same way you can install a custom home screen in Android. At the moment, however, this is all just speculation.
Minor tweaks: Right now, the hackers at XDA-Developers are digging through the leak in a hunt for other changes. The stuff they've discovered so far includes nature-themed emojis, auto-complete in the dialer (a feature already found on many non-stock Android phones), and lots of bug fixes. There's talk of new widgets and a modified Roboto font, but no specifics.
All in all, these are small changes, but they still make for an important update that will help Android become a cleaner operating system. And there's always a chance Google has more in store. We'll probably find out all the details on July 24, when Google is expected to announce a new Nexus 7 tablet.