I've worked with Sencha frameworks for 3 projects over 5 years. There is definitely a love-hate feel about it. The first project was working with it through GW

I've worked with Sencha frameworks for 3 projects over 5 years. There is definitely a love-hate feel about it. The first project was working with it through GWT. Views are built imperatively with Java. I didn't touch any JavaScript, HTML or CSS. Java kept all the types in check. Things are smooth. The second project was working with it JavaScript, after I've gained a year of experience working with HTML and CSS. Things are hard. Layouts are confusing. Seemingly simple stylings are hard to control. The third project is where I am now. Although we're still using the Sencha framework, a lot of the components are actually custom built. I guess the only parts of Sencha we're using are class system, layout (only very sparingly), and touch interaction. Things are smooth. We're now considering the possibility of switching out the full Sencha framework to Ext Core. This is where I say that I wish there can be an open source fork of Sencha. There are parts of Sencha that are good (class system, MVC, touch interaction) and there are parts that are bad (large component library that most people don't really need). A large part of the Sencha framework is actually the component libraries. If these are stripped out, I think it's possible for it to be smaller than Ember.