It is different for everybody I think, I mean happiness, the mission you gotta fulfill. Remember the soul-plane is not a phisical one, it exists outside time and space. You can see EVERYTHING from there, everything that cannot be percived with your current means.
You can see the society, the people one-by-one you can see everything from there, but the hard thing is that you loose all your memories when you are born so you won't know what you have seen "out there". I hope you know what I mean...
Happiness is something that is different in every case. Happiness could be to gather lotsa cash, or just have a cup of tea with you beloved one... or just see the world for a second (remeber the terrible child deaths
) I think I summarised it all...