If ever there's anything to shout about in an update, you can be sure an announcement would be made on these forums by the social media team.
Most updates are to fix issues that are often described on these forums already, or to support new features that will be announced when they're enabled (so wouldn't be included in release notes anyway).
(I'm a big fan of release notes myself - I like to know everything that is going on. I don't directly work on set top box though, so I'm not in a position to post them)
