I just finished "Heavy Rain" and here's my thoughts on it:
HR reminds me most of those old Sega CD FMV games where the action would play out and the player would be prompted to enter a command at a given time, essentially making a large amount of Quick Time Events. In fact, at times HR seems like what Sega CD developers were striving for in terms of a story created with human characters that a player could interact with.
I realize that to many the preceding paragraph sounds like an invitation to NOT play this game, but even with all this, HR is a very intriguing and immerse game that everyone with a PS3 owes to themselves to at least play. The acting is very well done, with a few exceptions, like the two "twin" boys who somehow have completely different accents, or the Irish looking cop who's voice was transplanted with that of a standard Italian cop from any given Law and Order episode. The control scheme of simple gestures with the analog stick and QTE heavy emphasis take little time to get used to and help to keep the story moving at a decent pace after a rather slow first quarter of the game. There are multiple endings, but odds are you'll beat the game once and then just use the chapter skipping tool to go back and replay certain sections to see what would have happened if you chose to leave the creepy house as opposed to stabbing the owner in the chest, or if you're a trophy whore and want as many as possible. Or, like me, you have a new baby at home and God Of War 3 is coming out next week and you need to free up a slot in your Gamefly queue.
Overall I highly recommend this game, especially if you're looking for something off the beaten path. There is a lot of potential for similar games of this genre, and this is a game you won't soon forget. It won't pull in any awards for graphics or innovative gameplay, but it should pull at your heartstrings, which is something many games fail to do nowadays.