I'm really excited that the final release of Ext JS 3/ is here, along with a preview of the Ext JS Designer application. This is built on top of Adobe AIR and allows developers to piece together their Ext JS app with a rich UI, tweaking configuration options and embedding components as required.
To my knowledge, there is no other JavaScript framework approaching the richness of Ext JS, and this designer takes it to the next level. I'm extremely excited about what the brilliant Ext JS team has in store for the future.