What a fantastic concept, having the PSP & PS3 used together so you can use the PS3 controller to play games on the PSP and have extra content added to a game.
Hopefully this will be a feature in many new games.
I think more people would use it if you didn't have to have both games as in the above example, but maybe download a few files from PSN to your PS3. It would definitely benefit those games that aren't released on PS3.