I honestly don't think the Christians can really answer this question. Although I would say that ever since the beginning of humanity, there was ALWAYS some conception of the "paradise"; a life after death that's better. According to Christian doctrines, that's probably an oral tradition starting with Adam and Eve talking to Seth about Eden...
And in the Christian perspective, being with God is good, so heaven would be full of that. What irritates me is what irritates you, DV. The idea of an eternal sermon is rather non-heavenly. I hate it how Christians say heaven is going to be like that...it automatically turns people off. They too often dont really step into the non-Christian perspective and speak on THOSE terms...
Where God's gonna rule exactly? Well, probably not on earth since Revelation says earth is gonna be a smoking crater after the end times...but I toy with the idea that God's heaven is comparable to a higher dimension that cannot be accessed or imagined by 3-d humans...that's a nice place for a God to rule, wouldn't u think?