God is never disappointed, because to be disappointed one has to have a certain level of ignorance! This is why we must know the character of God in our lives. When we know Him we never see disappointment but rather we see His government of grace in our lives and the lives around us. Because of grace, anyone come to Christ with a broken heart and empty hands. We watch in great amazement as a life is changed from glory to glory. Never seeing failure or shortcomings but seeing grace and truth applied and lived out in someone's life. But Satan would love for us to be ignorant of the plan of God and lacking in the understanding of the limitless possibilities of grace. Is this too much Grace? No, for where grace is, truth is right alongside of it. Grace is not grace without truth. For it would not be grace if it were cheap. But this is a gift of God paid with the highest price which makes it so holy.
The story of Jonah is full of disobedience and disappointment. Because Jonah refused to think with God and lose himself (meaning his own prejudices and lack of love for people), one could say that God was disappointed with His prophet. But I think the book of Jonah shows the entirety of God's plan of grace - not just for the people of Ninnevah but for Jonah as well!
Where the natural man sees disappointment, the spiritual man sees the eternal and is comforted.