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An interesting list of charting libraries including D3, Highcharts and Google charts. His conclusion is in line with my thoughts so far (and mine are based on far less comparisons): "It now depends on you to select the best charting library for your future projects. Developers who like to have all the controls over their charts will definitely opt for D3.js"
Florent Daudens created a vis for #knightD3 with exactly the two things I was looking for!
Adding tooltip consisting of multiple lines:
Adding labels to axis: