Sencha improved performance with Ext JS 4.1, but when it comes to optimal performance of Ext JS-based applications, that's only part of the battle. The rest comes from optimizing applications for performance, which often includes making a few changes so your code can take advantage of Ext JS enhancements.
Our webinar from February 16th, 2012 shows off some performance tips and tricks when working with Ext JS 4.1. Hosting this webinar were Edmund Leung, Don Griffin, and Nige "Animal" White.
Read more: sencha.com/blog/optimizing-ext-js-4-1-based-applications