While the main quest line is roughly the same for everyone, our experiences with the game have varied quite a bit. Connor likes to watch me play so he can find the treasure chests that I tend to ferret out, while he has fought against giant monsters that I haven't even seen. Currently, Alex has progressed the farthest in both main quest and storyline as she often plays while everyone else is sleeping or at work and school. I'm hoping to get the bulk of my playing done during the upcoming spring break, but we will have to see what my coursework has to say about that.
Not only has the game led to interesting conversations between family members, I actually think that it has helped me sleep better. Thinking about the game as I lie in bed puts me into a near meditative state that helps me drift to sleep with generally pleasant thoughts (despite the lonely nature of the game). In short, I highly recommend it; just make certain you work out an agreement between the people who want to play.