All i know is:
People react to you by what you chose to do,
You can have enemies (Rivals) and good friends both of which have questlines (sidemissions)
People go about their daily lives doing what the are scripted to do, with some leniency of other things happening/character choices.
Its my understanding that no one playthrough will ever be the same (as with most of bethesda's games)
Thats all ive heard/can remember right now..