Ranked in these QuestionsQuestion Ranking
Pro Easy data binding
Pro Easy to learn
Has a low entry barrier and an easy learning curve. It's especially easy to learn for beginners.
Pro Legacy browser support
Supports a large number of browsers, including IE6.
Pro Built in templating
Bindings in Knockout can also be used to control the generated structure of the HTML. There are bindings provided to allow for iteration and conditionals. The structure of the html reflects the structure of the data so iterative elements are bound to arrays in the data model. Having the HTML structure maintained by bindings keeps the templating simple, easy to read, and maintain.
Knockout also allows for string based templating so you can use whatever templating library you prefer.
Pro Great documentation
The excellent tutorials with built-in exercises are a great learning experience, even for people without prior MVVM and data binding experience.
Pro Dynamic models help with keeping the code simple and clean
Models in Knockout can be watched to keep the page data up to date by using observable objects. The observables notify Knockout when data is changed and automatically updates the page when this happens. By having Knockout maintain this relation, it keeps the front end code cleaner and simpler, and by enforcing a consistent pattern with observables the methodology can be more robust.
Pro Lightweight and plays nicely with other libraries
Pro It's only a library
Knockout does one thing, and does it well. It doesn't try to take on more than one area. It does MVVM data binding and that is it.
Pro Very flexible
One can do a lot of things and it keeps self references and other types of loops under control.
Pro Simple manageable modules
Using components is a great way of breaking up large modules into simpler ones.
Pro Extremely simple to implement.
To get started is extremely simple. It has a low learning curve.
Pro Seems to be quite stable
Even the most complicated GUIs are bug-free most of the time.
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 Webix Jet
The webix Jet library adds all the required features for SPA development (routing, template loading, ...)
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.
Con Seems to be dead
KO has been stuck at version 3.4 for a long time, and there's not a lot of community activity.
Con Can become complex once the application grows large
Knockout leaves the application structure to the developer and it can become quite complex and unmanageable in the hands of a beginner once the application grows large and complex.
Con Two way binding requires a little extra work
When allowing users to edit existing data, the two-way binding of observables means you'll need to have to save original values before they're edited, to make comparisons or revert if the user cancels the action.
Con Slower than others when amount of objects grows
Knockout has a bad performance when the dealing with large amount of objects. You can see more here.
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.
Con Commercial license
It's not free for commercial applications.