Would love github to add social features to opt-in to communication from maintainers. There is no good way today to email changelogs to your users.
[EDIT] Answer appears to be "yes, there is" (append ".atom" to the releases URL for a repo) with the caveat that the handling of pre-releases is less than ideal.
I used to use watch but I could care less about every individual commit on anything other than projects I'm actively working on.
Watch is not a good substitute for a way to learn about important changes on an infrequent, regular basis (i.e. once a month emails).
Email is the only reliable way to send/receive important updates for any meaningful project.