The Official PlayStation Blog had a live Q&A chat with Nate Fox,Game Director, and David Meyer, Programmer, from Sucker Punch. Here's what we know about inFamous based on that chat:
* The idea for inFamous came from mashing a bunch of different ideas in order to create Grand Theft Auto with super powers.
* inFamous should take you about 25 hours if you are going for the Platinum Trophy.
* All kind of super powers were considered before electricity was chosen.
* Empire City is over 100 hexes, each hex being the size of one Sly Cooper open world exterior.
* Sly Cooper references are scattered around the game.
* There are different cutscenes for different game styles - good and evil.
More interesting facts in the link.