I've run into this problem, too.
The workaround I found was to use a can.compute() which allows you
to replace the list completely. It means you must access the attribute
differently (object.users() instead of object.users) but most of the
time you are working with mustache templates and there it is the same.
See updated example that works: http://jsfiddle.net/6A7PW/2/
