In case you haven't seen, User:Rillke on Commons has implemented a (default-on!) gadget that makes it possible to subscribe to notifications of different types, e.g. policy changes, new features, etc. These are shown as watchlist banners and upon login.
Here's a screenshot of the "subscription" interface: http://i.imgur.com/gdImENz.png
IMO that type of gadget lends supports to the notion of shooting for a subscription model to be ultimately integrated with Echo so that users can get standard read-once notifications about things they care about while keeping the core UI clutter-free.
Erik
-- Erik Möller VP of Engineering and Product Development, Wikimedia Foundation