While I am actively learning D3 itself, I really like the style of this library and its abilities. It makes almost 100% of the same design decisions I would make when plotting the kinds of charts it does. I've been looking for an open-source project like this for ages. I know about a lot of others (like nvd3) but never quite felt like anything provided the level of interaction (specifically hover states) I wanted. I'm excited to give Metrics a shot.