@wchigo: Well, I can tell you that I played all of Demon's Souls using my DualShock 4 on the PS3. It's pretty easy to set up. Go into the PS3 menus, and there's an option for managing accessories, or controllers or something. Anyway, in one of those, there's an option to scan for new devices. Get that going, then hold the PS button and the Share button at the same time on the controller for a few seconds, and it should sync up the controller to the PS3. Granted, you'll have to go to the controller settings and set that controller to be controller 1, and you won't have 100% functionality. There's no rumble, no motion controls (not that Demon's Souls has that) and the PS button won't do anything in game, so you'd need to have a DS3 handy for anything that requires that. But as for in game, it works perfectly. The Share button has the same functionality as the Select button.
If my explanation is...lacking, or accidentally incorrect, you can find the information easily online. I should add that this doesn't work for all games (damn you Burnout Paradise), but it works in most PS3 games. And once you sync it to the PS3, it stays synced, so you can hit the PS button to turn the PS3 on (don't ask me why it then doesn't work once the console is on, I don't know). And if you want it re-synced to the PS4, just plug it in via USB and hold the PS button for a few seconds.