Most of the [examples](https://github.com/mbostock/d3/wiki/Gallery) provided are by the author, but there's also a great community writing plugins and more examples.
Ranked in these QuestionsQuestion Ranking
Pro Huge number of examples online
Most of the examples provided are by the author, but there's also a great community writing plugins and more examples.
Pro Large community
D3.js is a very popular tool with an active community, resulting in plenty of learning resources and fast responses to questions.
Pro Doesn't require a proprietary framework
D3's emphasis on web standards gives you the full capabilities of modern browsers without tying yourself to a proprietary framework.
Pro Versatile library for manipulating data on the DOM
Pro Very flexible join paradigm
Can be tricky at first, but once learned, data manipulation and binding can easily generate complex visualizations for massive amounts of data.
Pro Great for highly interactive scenes
D3.js offers incredible levels of interactivity.
Pro Backwards compatible
D3.js is intended for modern browsers, so supports IE9 and above (IE8 with an additional library) as well as all the other modern browsers.
Pro Extremely simple to implement.
To get started is extremely simple. It has a low learning curve.
Pro A lot of widgets
Webix is one of the most extensive UI component libraries, second only to Sencha ExtJS. Not only considering the number of widgets, but also the API methods for manipulating these widgets.
Pro Webix Jet
The webix Jet library adds all the required features for SPA development (routing, template loading, ...)
Pro Great support from the webix team
The company behind webix is really quick in answering any questions you have on their forum or via email.
Pro Awesome responsive material skins
Great design and icons pack.
Pro Seems to be quite stable
Even the most complicated GUIs are bug-free most of the time.
Pro Mature project
Regular updates and releases.
Con Steep learning curve
The complexity and flexibility of D3.js results in it being a time-consuming tool to learn for many users.
Con "Selections" are elegant, but somewhat hard to grok
Selections are core to working with D3 beyond the basics. They're powerful and useful, but require new developers to get up to speed (e.g. set aside 30m to read and digest: https://github.com/mbostock/d3/wiki/Selections) and if used in the context of a larger application will result in a portion of the code using different patterns than the rest, requiring a translation layer in between.
Con Commercial license
It's not free for commercial applications.
Con Not very popular
Not really a reason to not recommend it. But it has still a small user base. It deserves a lot more attention.
Con Not modular
The library is not modular (except for some additional more complex widgets). If you only need a few widgets, you still need to include the entire library.