As you'll see from the RGraph documentation there are lots of advantages to using RGraph such as:
RGraph uses the Creative Commons BY-NC license. This means that if you want to use RGraph on a non-commercial website then you can - no permission necessary! If you need to make changes to it then you can also do that no questions asked.
Rendering times can be measured in milliseconds so the charts won't slow down your page. There's a substantial section in the documentation about speeding up your pages. Many of these performance tips can also be applied to pages that don't even use the canvas tag.
If you have an issue with RGraph you can send an email to the RGaph support team using the support request form.
All of the supported chart types can be used in conjunction with AJAX, JSON or both. There is specific functionality available to make working with these technologies easier. There are examples of AJAX in the documentation and the download archive and as of July 2014 the whole of the RGraph configuration has been updated to support JSON better.
All of the charts support interactive features such as tooltips, CSS animations and visual effects, context menus, adjustability, zooming, annotation and custom events.
The RGraph drawing API allows you to add interactive elements to your charts such as rectangles, circles, polygons, images and extra axes. These allow you to customise your charts and add extra interactivity.
The comprehensive RGraph documentation is both up-to-date and has plenty of easy-to-follow examples and simplified walk-thrus.
...to name a few. You can also combine different types of charts (see the examples for more).
All the charts and features are documented with examples and code that you can use. The HOWTO guides walk you through doing common tasks step-by-step with more example code.
The full source is included in the download and you're free to make changes to meet your needs. The API is documented and there are several basic examples to help get you up and running.
If you have a suggestion for a feature that you think would be beneficial to RGraph then you can suggest it by using the support form.