Here's what's up: Google is adding restricted profiles, which are basically just more comprehensive parental controls. It forces an app to behave differently, based on what a parent has set up. So if a child is playing a game, you can say he or she can only see a couple of levels, for example.Restricted profiles also let you set limits on transactions, or web browsing, or other things you're using your device for.
Android 4.3 also features some Bluetooth updates that let you pair an Android device with low-power gadgets like fitness trackers. Got a FitBit? You can hook it up to your Nexus 7 to monitor your performance.
Additionally, Android 4.3 is getting a refresh on something called Open GL:ES 3.0. It's a big boost for graphics that mostly applies for gamers. It'll make everything on screen look better, more detailed, and render quickly in native 1080p resolution. More here.