Where does Dennett claim in Consciousness Explained that the mind is a Von Neumann machine? I think that in the book he calls his model a Joycean machine; but by claiming that the mind amounts to a computation he subscribes to the consequence that it may be implemented in principle by any universal computation device, be it a quantum computer, a Von Neumann computer, or a mechanical implementation of a Universal Turing Machine built from cog wheels and running on steam, and it does not matter if the specific architecture that he is contemplating now has changed in the last 20 years; ask him in 20 years and he may have another theory in mind;
there is a lot of other good and bad stuff in the book that make it worth while reading, or at least going over; for example how not to treat other opinions (Dennett is often ridiculing and patronizing colleagues, sometimes it seems that he does it as a technique to make his arguments seem more convincing), and on the other hand his writing is always a beautiful example for communicating philosophy and interesting ideas clearly without using cryptic and highly technical jargon. and finally, especially if you disagree with him, it is good to read it as a challenge for ones ideas.