A bit of the shame on the interactivity: "If you are looking to add interaction as a layer to charts, Chart.js is not the library for you. A better option would be using SVG, as this will let you attach event listeners to any of the elements in the chart, as these are all DOM nodes." Most charts are far more useful with rollovers to let the user interpret the data. I'd say this is a must have for most anything where…
I have a little application with charts. I was using jqplot but IMHO it was too heavy and I started googling for a lighter solution. I found flot. flot is based on canvas and has user interaction. I don't know how it is implemented (btw flot is mit licensed) but it works. it's a shame that this library doesn't support user interaction