My problem with D3 is that I can never just sit down and say: "This is what I'm going to make, its going to be the coolest visualization in the world, NY Times is going to hire me" It is really the most counterintuitive library I've ever had to deal with. How about you?
Find the type of visualization I want to make on http://bl.ocks.org/. Start with that code, understand the steps taken to build it, then tweak each step / the data source until I have what I want. Works fairly well and helps you learn the library, without having to roll everything from scratch.