Moving an element from one shadow root to another appears to break the binding and the xxxChanged property function on the moved element.
See http://jsbin.com/ayiwem/2/edit for a trivial example that tries to isolate the issue. This shows a simple counter that increments a "count" property when clicked. When that property changes, the visible click count is updated, and a countChanged function is automatically invoked (which logs the change in the console). Clicking this button works as expected.
The second instance of the counter is hosted inside an element that creates a new (second) shadow root, and moves the counter into the new shadow subtree. As of last month, that code worked. That is, a click on the second button incremented the visible counter and invoked the countChanged function.
This code appears to have been broken by polymer-all check-in 72025651de9cf0892fd8b0afb7c91147bc9c1850. I'm wondering whether the new state of things is expected, or a bug.
Updated example to track Polymer changes (<element> is now <polymer-element>, etc.): http://jsbin.com/ayiwem/4/edit
This should be fixed in the master branch by Polymer/platform@160cf93
Sweet! Thank you.