They offer thousands of different kinds of charts. You dream it and they have it. On top of that the interactivity of the charts is intuitive. You can make a lot of really high quality graphs in a very short amount of time. I usually make an image of the chart and embed it with the HTML so it shows out as a popup. Very very sleek!
You should be comfortable with basic scripting if you want to make us of this. Also it does not let you download the URL therefore its workable only when you are online. Therefore, we have now shifted to using Plotly and AnyChart.
Learn basic scripting before you can take the complete advantage of this tool. Its really powerful and can provide real time intuitive charts if you know a little bit of scripting.
I use them to make business plan projections, and analyse and plot a lot of sales and research data.