Around that time, I noticed the new modular repos on the d3 Github org coming together, and have since been watching with great anticipation. I'm glad to see d3 evolving for a new world where its excellent, fine-tuned collection of math and drawing functions work in concert with your rendering framework of choice.
Scroll to the bottom for the wrapper class. Please excuse the coffeescript.
It's not possible to put a sector back into the piechart by clicking on it again. So once you clicked on any sector, there's no way to go back to the original chart state.
Using up/down arrows to change selection in comboboxes doesn't update the graph.
Tree Chart has no animation on leaf expansion/collapse, so clicking, for example, on Grandma results in the graph transformation that's abrupt and not immediately obvious. There's also no way to tell collapsed nodes from those without children (leafs).
Sankey Diagram could use some fade transitions to make highlighting less jarring.
I think it helps if you just understand the mental model that d3 is going for. Clearly tons of people are able to do good work with it.