Just a quick answer - I am actively developing with ExtJS for about 3 years now. It depends on what product are going to build. I always say that ExtJS is great

Just a quick answer - I am actively developing with ExtJS for about 3 years now. It depends on what product are going to build. I always say that ExtJS is great for 'excel on the web' kind of applications - desktop like apps. The grid component is unbeatable, so is the layout system (which limits the CSS nightmare pretty much). However there are caveats of which mostly discussed is steep learning curve. It's true that it takes some time till one uses ExtJS in the right way. Blog posts like this one are a good read before starting new project http://www.sencha.com/blog/top-10-ext-js-development-practices-to-avoid http://www.sencha.com/blog/top-10-ext-js-development-practic... I have no experience with KendoUI, but from what I saw it is the closest match to ExtJS in terms of developing desktop-like JS apps. And it's free. Edit: looks like KendoUI is not free anymore.