(Haven't read it yet, BTW)People trying to make a point often seem to invent an "prevailing opinion" to argue against. I don't think that many people really think computers are omnipotent. Good idea for a book though.
Another good reason for tackling this point is that understanding what computers *aren't* highlights some really odd things about what minds *are*.
Books like this one, "The Emporer's New Mind" and "Godel, Esher, Bach" do do seem to imply some truly wierd things about the capabilities of human brains.
Incidentally, does anyone know of any research into analogue computing approaches to artificial intelligence? It seems fairly clear from the maths that nothing which is limited to carrying out tasks a Turing machine could perform will ever shed that much light on the nature of the mind