Sony just announced the PlayStation 4 here at their PlayStation event in New York City, and before they're showing off the actual console and demoing some of its features, they're taking the time to explain what they call the five key principles of the user interface: Simple, Immediate, Social, Integrated, and Personalized.
First off, Sony wanted their user interface to be simple. For instance, they want powerful functionality to be just a button press away. On the PlayStation 4, Sony has said they decreased the lag time needed between the content wanted and the gamers themselves. Sleeping and powering up the console is also another thing they wanted to be simple. You can easily sleep the console with the controller, and wake it up with the controller as well, from where you can continue where you left off in a game right away. This also fits in with their "Immediate" key principle.
The social aspect of the PlayStation 4 UI involves a lot more sharing features. Users will be able to quickly and easily share 10 seconds of video, as well as trim it and upload it for sharing to friends. Gamers can also live-stream their gameplay, and friends can take over for you if you need help with a certain level in a game. The social aspect will also be "highly integrated," and users will be able to use mobile apps to stay connected.
Finally, personalization is the last key principle that Sony is focusing on in their user interface. the PS4 will get to know you in a way, and will keep track of your likes and dislikes and will learn your habits to personalize the console. The PS4 will automatically download content that it knows you'll like. Essentially, the PS4 wants to decrease the amount of time needed to download a game, meaning that PS4 will download games for you before you even think about it.