The D3 chart implementation is based on the SMWAggregatablePrinter class which defines values as a simple array of [label, value] pairs which means that as for the moment data series are not possible and not planned. D3 chart corresponds to a similar approach held by jqplotchart/jqplotseries.
Available examples are self-explanatory and easy to understand (I tried to make inline comments where necessary) and I would encourage anyone with a vital interest in extending SMW/D3 integration to coordinate efforts.
A more comprehensive and elaborate integration is planned with D3 graph (which I have no idea when I have time to work on as part of the SRF D3 integration).
Another example that uses D3 is called wordcloud which will be deployed with SMW/SRF 1.8.