I had some complex JS plotting to do as part of a client project, with axis navigation, color changes, discontinuous lines on time-axis scatter plots, custom markers, and custom gridlines. I scrapped my initial approach and switched to Highcharts, saving a lot of time compared to building the plot directly in D3.
By default you get a great plot, and with a well-documented API you can customize literally every aspect. Congratulations to the team on the launch of the new version!