I rather they allow PlayStation Portable games to be used on PlayStation 3, it would be simple, cut and dry, just let me purchase it on PSN (whenever that returns). During the hack it was learned that Sony set it all up, but never did it because they want to artificially extend the platform's life. Same with PlayStation 2.
I would be fine with spending just a bit more money on a game to have it work on all available platforms. Supposudly Microsoft is going to do this with small games that can work on Xbox 360/Games for Windows/Windows Phone 7, but I can understand that because no one knows what the last two are.