Otherwise, the gist of the change is this: Instance traits have the ability to automatically adapt objects on assignment, but this feature is OFF by default (you need to specify "adapt='yes'" to activate it, or better use the Supports and AdaptsTo trait). List traits, instead, had automatic adaptation ON by default, which caused inconsistent behavior in some corner cases. We changed that so that it is OFF by default.
It is a technicality, really, but if you rely on automatic adaptation you may want to make sure you explicitly turn automatic adaptation on if you need it.
All the best,
-- Pietro Berkes Scientific software developer Enthought UK