those are some cool looking diagrams... Something to aim for I have been thinking about using canvas because like you point out, its faster. However I had not worked at all with the canvas and new something about d3.js and svg. d3.js allowed me to use some dragging / events, which I could not have build myself when i started out with this project. That was simply what tipped me in to going with svg. To late to change now...And although there are times when speed is an issue when using the map, its got more to do with some inefficient programming from me.