During its E3 conference, Sony talked business and showed games. Leaving some of the more mundane - but no less important - stuff to come out after. Stuff like this video, which shows the system's user interface.
We can see how the PS4 swaps between programs (like a phone), how the share button works, how you can download certain parts of a game first, how the PS4's keyboard works, how its party sharing works, how you can stay connected even on a mobile device...you get the idea. The nuts and bolts.
Playstation 4 - User Interface Overview Promo [YouTube, thanks Matthew!]