Graphviz is great if you either want to automatically generate diagrams of huge graphs, or if you care more about structure than appearance.
But creating pretty diagrams with Graphviz/dot is an exercise in pain.
I love seeing more of these tools, and plan to integrate several of them in the scripts I use to build my blog, not to supplant the cases where I use Graphviz, but to augment them for the many situations where I want to do diagrams that need more precise control than Graphviz does.
(My personal Graphviz self-flagellation exercise involves an XSL file to convert the SVG output from dot to something prettier: https://github.com/vidarh/diagram-tools )
I use Mermaid [1]. It has similar layout algorithms as Graphiviz/dot, and is significantly prettier out of the box.
Mermaid has multiple renderers (including a client-side JavaScript one), including SVG, so you can trivially style all your diagrams using CSS. It can also process diagrams embedded in Markdown.
That said, just like Graphviz, its weak points is "messy" diagrams. But it supports subgraphs, which can help making them cleaner.
But creating pretty diagrams with Graphviz/dot is an exercise in pain.
I think Graphviz really needs a better routing algorithm - with many vertices and edges the result starts looking like a mass of tangled hair. Something closer to the routing algorithms used in PCB design[1] would be far more readable.
I can beat that - I had an ASP.Net application that queried a set of SharePoint lists to generate 100s of diagrams giving details of what applications were used for different business processes at each site in a large multinational.
It did work but there was a lot of tweaking of the process to create the dot files....
But creating pretty diagrams with Graphviz/dot is an exercise in pain.
I love seeing more of these tools, and plan to integrate several of them in the scripts I use to build my blog, not to supplant the cases where I use Graphviz, but to augment them for the many situations where I want to do diagrams that need more precise control than Graphviz does.
(My personal Graphviz self-flagellation exercise involves an XSL file to convert the SVG output from dot to something prettier: https://github.com/vidarh/diagram-tools )