If something is working for you, don't change it. ExtJS is a fairly large framework and replacing it with something 'better' would have a large cost for your or

If something is working for you, don't change it. ExtJS is a fairly large framework and replacing it with something 'better' would have a large cost for your organization. That said, my experience is primarily with coolite and versions 2 and 3 of the framework. I was working closely with another team using 4, which sounded better. ExtJS' main problem is that it does too much. It tries to replace jQuery, CSS, JavaScript OO frameworks and then adds it's widget/control and code structure on top of all that. If it just did the last one (maybe two), it would be a decent framework. I still would not choose it because I don't like how it gets in the way of API calls nor the control of event handling in versions 2 and 3. This last point has probably been improved in 4 with the introduction of an actual MVC structure, but I don't know for certain. In any case, using enormous object literals to configure and control everything from styles, events and actions made it both difficult to work with and test. Often times these blocks of code would exceed hundreds of lines. In short, ExtJS sets up developers to fail. Most of what it does can be written in jQuery using CSS classes far more concisely. It's strongest points were it's UI controls, especially the grids. I think these are the things where the framework adds value, the rest would be better served using more commonly adapted practices.