[eluser]OverZealous[/eluser]
I've definitely heard of ExtJS. I believe it was still fairly young when I started development on Zesty, but either way, I have not used it. (I just checked it out. It looks pretty slick!)
I truly recommend that you find the JS library that matches your needs, the time constraints of your project, and the size and scope of your project. A library like Dojo has a fairly steep learning curve, especially as you start developing your own widgets. You can see how complex Zesty is, and I have great plans for it still. (Up next is printing, followed by simple invoice management.)
