For the amazing price of "making the effort to click through a few menus," you'll get Kat from Gravity Rush and Emmett Graves from Starhawk for your troubles. Keep in mind that the DLC is only free for two weeks, at which point they'll revert to $4.99 each.
Even if you don't own the game, log into the PSN and download the license to the DLC anyways. Who knows, you might play it at some point, and extra characters will come in handy!
Personally, I can't wait to try out Kat. Gravity Rush is one of my favorite games of all time, and a lot of that is due in part to how likeable she is.