I'm kind of having the same problem with the 'itemtap' event. I have a TabPanel with 'cards'. One of them is a Container and inside it I have a List. If I don't set the Container to layout: fit it won't display any item. For the List I don't specify any layout. However the 'onItemDisclosure' event is fired when I click on the arrow buttons at the end of the items. This is not much of a problem since I am able to navigate back and forth but it'd be nice to have the itemtap even also working, or understanding what I'm doing wrong.
I'm using the latest version of Sencha Touch (2.1, free commercial version) on latest version of Google Chrome (23.0.1271.95 m).