At the time that blog entry and code sample was published, it worked with the current beta of AIR. However, the latest version breaks some key things. Adobe is aware of the problems (with the help of Jack) and we all (and many other communities wanting to use AIR) are hoping they get fixed for the next beta release.
Jeff Howden
Ext JS - Support Team Volunteer jeff@extjs.com
Any and all code samples that are authored by me and posted on the Ext forums or website are hereby released into the public domain and I release anyone or entity of liability by using said code samples unless explicitly stated otherwise.
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In case anyone wants to use the Simple Tasks app and already has AIR beta2 installed, the adobe labs downloads page has the beta1 download available which can be installed even if beta2 is already installed.