Developing Ext JS 4 applications using Eclipse is really painful. Period.
Copy-Paste is a most often used technology in any project. For some reason, when you try to select some lines of Ext JS 4 code to copy and paste it, Eclipse starts huffing and puffing and becomes unresponsive. In fact, I have seen several developers forced to kill eclipse.exe and restart it.
Working with MVC in Ext JS 4 leads to creating number of JS files. The build process of the web application gets too slow. The more number of JS files, the more time it takes for the build an application in Eclipse.
Though there’re tools that you can use to develop Ext JS 4 applications, I personally prefer Visual Studio. A trial version of the express web edition is adequate for this purpose. It’s lightweight and speeds up the development.
Eclipse is a not the right IDE for developing Ext JS 4 applications, but if your server application is a JEE-based one, it will hurt us.