Well, it's not exactly addressing your wish, but the preview from Game Informer
does touch on it:
# In previous GTA games you were like a slave because you had to constantly take orders from people when doing missions. There is still an element of that in Grand Theft Auto 4, but you can also choose how you want to spend your time, for example "I want to hang out with him and her. I want to hang out with this guy because he always has fun things to do." Call him up and maybe you can hang with him. Maybe he'll answer. You have a lot of choice over what you want to do.
# In GTA 4, Rockstar is giving its players more freedom, more choice, and more sense of control over their destiny - the structure of GTA4's storyline is quite different to it's predecessors as it can be told in a number of different ways. You can talk to people in person, by cell phones, and there are a bunch of other ways of giving the player information. In general it's a different experience, with new ways of interacting with the characters and the game world.
There are some other really good tidbits in that interview, worth a peek.