Having tried to think about how to map Graphviz (language parsing, styles, and layout) onto our graph drawing offering, I'm not sure I can agree here. The dot graph description language itself is fairly simple (-ish). There are a few nasties like the HTML record support, which can be annoying to support, but overall that part isn't so bad. When it comes to laying out the graphs and rendering anything Graphviz has so many unique features that it can be a lot more work.