I think that Haroun experiences a great deal of growth in the story.  At the start, he is a fairly ignorant child, who does not understand the larger implications of what is happening with his father and the nature of political control that is involved.  He begins to assert a greater voice in helping his father gain back the ability to tell stories, to resume his role as "the Shah of Blah."  He also understands how important his father's role exactly is.  At the outset, Haroun does not understand why his father's ability to tell stories is important at all.  Yet, when he has to assume responsibility for assisting his father reclaim his voice, Haroun understands the true nature of why telling stories is so important.  He also begins to understand that without storytellers, those in the position of power are able to exercise greater control over an unsuspecting public.  This is a position that Rushdie himself believes and for which has given great sacrifice.  The poignancy in this is that as Haroun understands and moves towards his father at the end, Rushdie hopes that his son, Zafar, will do the same with him.