I like the idea of the 'now' namespace because it is about as simple as you can get – the only required element is
<now:content> – but recognise that it may not meet everyone's requirements. Still, we have to start somewhere.
One of Bix's criticisms of Robin Sloan's Spring '83 is that it expects you to create specific content for your 'board' rather than reusing what you might have already written elsewhere. Using RSS as the distribution method means you can repurpose what you have already written. It does, of course, require some behind the scenes coding to get the required information into the feed but once it's set up it is automatic.
Responding to Bix on GitHub, I suggested that
<now:content> could be replaced by (or even become) a container element holding multiple items. This would support the scenario he suggests. How reader apps would consume and present this information is another matter. The namespace proposal is purely about the sharing of updates; what clients do with those updates is a question of preference but it was originally envisaged they would display the update content. There is, however, nothing to stop a client merely acting as a notification system but this was not the intention.
I have added a 'Further Details' page to the repository for more information and discussion.