Said says in the 1993 afterword that the only criticism he found invalid was the criticism based in bad faith interpretations of his main argument. The 2008 article is a clear example of that. He promotes a few examples of disagreements that he had about the text after publication that did allow for further knowledge production as opposed to reactionary polemics.
The main argument is basically that more or less starting with the Napoleon’s invasion of Egypt and through our current era (Said died soon after the invasion of Iraq in 2003 and wrote about it as well before he died) there has been a deeply flawed construction of the “Orient” through art, politics, writing, and other forms of communication and information production that initially was based in English and French Orientalists and then in the 20th century especially in American ones that attempted to define, delimit, and create the “Orient” where one doesn’t actually exist. Said’s repeated argument is that there’s no such thing as an essentialist understanding of the “Orient” or Islam of the Middle or Near East and Northern Africa, but instead there is a whole body of work and thinking instead. This body of work is actually what has been created, entirely separate from the actual people, spaces, and history and culture that they purport to represent. Using especially Erich Auerbach’s concept of representation, Said argues that it’s the representation itself that was created, not an accurate understanding of something immeasurably too complex to understand. This representation then becomes repeated and replicated and further fuels more representation. He just barely predates Lyotard and Baudrillard in their postmodern works (and he also bristles at a comparison with postmodernism because of the actual real-world geopolitical realities of the people being represented). These representations are not based in the reality of the people there, but in the writers and creators who formulate them. They inevitably lead to racism, power and control. And this process continues today.
He uses an extremely long list of different examples to illustrate this argument, but one notion I want to bring out is his concept of the “textual attitude” which involves the process of a text standing in for something complex and forming a sense of reality that the text cannot possibly justify or validate. This is most easily understood through Don Quixote’s understanding of the world in Cervantes’s novel as being based in the romances that he’s spent his life reading, only to find a world outside his library not remotely resembling those fictions.
Where Said falters a little in my mind is in his characterization of American Orientalism. He focuses primarily on area studies experts as the modern equalivalent, who have a technical knowledge that may or may not be accurate but is necessarily limited and dehumanizing. I think he misses an opportunity to recognize the ways in which the mythologizing of the West and the Frontier clearly had some very similar impact on US cultural imperialism in the 20th century. While those mythic impulses played out more specifically in places like the Philippines, Vietnam, Japan, and space, that drive most certainly influences US Middle East policy, something that I think would have been undeniable by 2003 at the very least.