I can't tell if everyone one is like that (I assume not), but I am extremely reliant on visualization, and I suppose Bret is also. I believe profoundly on it's power partly because it's the only way I can really get things done properly, which is why those tools resonate so much to me. I have a friend however that shudders every time I mention making programming more visual.
I mean, If I'm not visualizing something, I can perhaps find some solution in a logical way following some guidelines -- much like following a recipe to solve a equation or doing trial an error to solve an algebraic problem. But critically, I can't create this way. I may stumble unto something useful, but it's an entirely different process from creativity -- it's efficiency is so much lower that it's qualitatively different.
But my difficulty at that is not fundamental, I think. I believe you can be creative purely 'algebraically', but I have no experience with it -- but I do believe that some people have the same efficiency that I have when I think visually and perhaps stumble a little more when trying to visualize things themselves.
I do think this diversity is quite good, but that's missing the point. My point is that Bret's tools shouldn't be universally essential, but are probably universally beneficial. And for some people, like me, they'd be simply enabling.
To give an exaple: when I see a system of linear equations, I don't think of a bunch of steps to solve them and the number of cases that the solutions may look like in terms of constraints of variables an so on. I think of the Image hyperplane, which can be abstracted as a plane in 3D, and the Kernel, which may be for example a line not on the Image. Then instead I wonder if the Kernel is non-null, what funny things this matrix is doing to the vectors (are they rotating, contracting, and so on), or what are the invariant subspaces. I can answer most questions one could ask about such system, but it's a distinct way, I'm not sure if more efficient or not (and that may be up to the task).