Do you mean that the graphs don't look good? They layout seems good, to me. I have a Theory of Computation text so I have many, many such diagrams. I don't r

Do you mean that the graphs don't look good? They layout seems good, to me. I have a Theory of Computation text so I have many, many such diagrams. I don't rely on the graphviz output directly. If I have to make a graph where the layout isn't obvious then I write a .dot file and run it through graphviz, specifically, neato. I use that as a model for drawing it with a LaTeX tool (I don't use TikZ, I use Asymptote, but the point is the same). That way I get a pretty good layout, better then I personally could do without the guidance from graphviz, and a visual consistency to the diagrams.