John Piper presented some good arguments for “Why Expositional Preaching is Particularly Glorifying to God” at the Together for the Gospel Conference in 2006. Below I have highlighted some key remarks on expository preaching.
Piper quotes Arnold Dallimore (A George Whitefield Biographer) that the foundation of expository preaching is the “heralding God’s word from the kind of heart” that is mighty in the Scriptures, aglow with the great truths of the doctrines of grace, dead to self, willing to labor and suffer, indifferent from the accolades of man, broken for sin, and dominated by a sense of the greatness, the majesty, and holiness of God.
The preachers view of God is foundational for their philosophy of preaching, Piper argues “What you believe about the necessity of preaching and the nature of preaching is governed by your sense of the greatness of the glory of God and how you believe people awaken to that glory and live for that glory.”
God is revealed in His word, and “God intends for preachers to unfold these words and exult over them”- this is what Piper calls expository exultation. This is where passion in preaching comes from, exultation. When the preacher exults over the truth that he is unfolding it becomes worship, giving glory to God in heralding Christ through the power of the spirit.
This is huge, in essence what Piper is arguing is that the preacher should not only exposit the text (open, unfold, clarify, explain, display), but also exult over it (Worship through sharing the glory of the Gospel).
DR. MATT CAPPS 
Agreed. What I’m learning is, the preacher has to be honest about his/her own experience in order to get to that exultation.