1. The term "hedonism" means "a living for pleasure". If the chief end of man is to enjoy God forever, then we should live our lives for pleasure -- the pleasure of knowing God.
2. The term does not refer to a single, pagan philosophy but is a generic term that has been applied to a wide variety of philosophies that elevate the pursuit of pleasure. For the Christian hedonist, it includes the idea of pursuing the greatest pleasure, not in the short term, but maximized over eternity.
3. Many wise, old Christians have chosen to describe the Christian life in these terms. C. S. Lewis and Soren Kierkegaard are among them.
4. The term has a jolting effect. This is appropriate for a philosophy that has a life-changing effect on its adherents. Furthermore, this philosophy can be extremely threatening to nominal adherents of Christianity, since it focuses on the motives of the heart rather than superficial actions.
5. Although the word definitely has a pagan connotation in most circumstances, Scripture itself uses words with normally negative connotations to teach positive truth. For instance, Jesus compared himself to a thief in the night. He also commended the shrewdness of an unrighteous steward. Surely, a word that is in essence quite neutral can be used to express the truth that we should find our highest delight in God!
6. Finally, the word "Christian" as a modifier of the term "hedonism" signals loud and clear that this is no ordinary hedonism. It is controlled and defined by the Christian revelation, the Bible. Only by submitting ourselves to the authority of Scripture can we know what is everlastingly most pleasing.

For more information, I strongly encourage you to read Piper's book. Click here for more details.