We have been using Highcharts from version 4.x to current version 7.x. my overall experience is just awesome with Highcharts library.
Main advantages are below:
2. Easy to use because of coding standards.
3. Free documentation is available on official website.
4. It is free for non commercial usage
5. It support multiple axis design.
6. It is working on cross browser and don't need flash play at all and i love that.
7. We can export the chart as PDF JPG and in PNG format as well using one click. Review collected by and hosted on G2.com.