I just read an article on Christian Hedonism by John Piper. And I must admit, I think he's lost it.
He argues against Christian morality as a deontological theory. And to that degree, he's right. We shouldn't follow Christ because it is the right thing to do.
But should we really be following Christ because we want to get into Heaven?
By no means!
Hedonism, whether addressed from a secular or religious standpoint, is a self-centered point of view. Even if we take John Stuart Mill's defense* of hedonism and admit, as I am willing to, that true happiness is found neither in immediate returns or physical (lower) pleasures, hedonism still reduces the right thing to do down to what's best for the actor.
Piper argues that many places in the Bible address the rewards offered to the faithful in Heaven. And to be sure, Christians should look forward to the eternal Kingdom of God. But Piper's main flaw in the logical conclusion of this train of thought (which he conveniently avoids). By hedonistic reasoning, if we should do good deeds because God will reward us, than we earn our rewards and negate the need for Christ as Saviour. Sure, we can keep him as our Teacher and Lord, but his crucifixion becomes meaningless.
Why should Christians do what they do? Well, in all honesty, some, perhaps even most, Christians start their journeys because they want to get into Heaven, to avoid Hell, or because they were taught that "It's the right thing to do." A sign of true oneness with God, however, is acting the way God acts - acting out of Love. It's not something taught in ethics classes and the classical ethicists have not written about it. But it's why Christ did what he did. And we are called to follow him.
*For more on this defense, see Mill's Utilitarianism.