PlayStation 4's interface discussed in detail by Sony's Yoshida.
Yoshida reflects on the gamescom demo, (quotes from the PS US Blog):
“What I showed was only a small portion of the UI,” he explained. “Obviously the system software is still in development. We really wanted to show off the social aspect of the UI. The minute you boot up, you’ll see all the information about games you own, what your friends are doing, whether there’s any new DLC coming out, or if your friends have shared a video or screenshot. And you can also spectate anyone playing PS4.