During an interview with G4TV (linked above), Quantic Dream co-CEO and writer/director David Cage reveals some details of the an upcoming Heavy Rain PS3 demo, his concerns, and why a demo will be important for gamers to try to gain a better understanding of Heavy Rain's concept.
To quote: "G4: Have you considered releasing a short demo via PSN of a scene such as the Norman Jayden junkyard fight, to convey what the game is to gamers who don't follow enthusiast media?
DC: Definitely. We are currently working on a demo, which is a real challenge. Finding one scene that can convey what we are trying to achieve with Heavy Rain is something really difficult. If we show an action scene, some players will think that this is what Heavy Rain is all about, and it is the same thing if we show an exploration scene.
The problem is that each scene of the game offers contextual game play, which is something very difficult to explain and convey in a single demo. Demos are often a double-edge thing: if you don't release one, players may think that you have something to hide. We also know many good games that ended up not being massive hits because the demo could not convey the quality of the game behind it.
Because Heavy Rain is a new concept and since many gamers will want to check what it is before buying it, we will be releasing a demo. We just need to find the best scene for it."
I completed Fahrenheit (also known as Indigo Prophecy) on the PC and thoroughly enjoyed it, i am hoping that Heavy Rain is just as good and would probably have bought it without a demo being available.