By playing with the number of lines and their color, distance, thickness, opacity and dashing, the possibilities to style the map are really nice.
Using the jsts library was the easiest way I found, altough the integration with d3js is not easy. Maybe using WKT instead of GeoJSON as an input would be nicer. Also, if your geometries cross the -180 meridian, the buffer lines go crazy. This should be fixed too.