So my angle on this is to have a client that is completely auto-populating. It's not necessarily something that will be useful for everyone, I admit (and is a slightly different interaction model than we usually use).

But I think it'd be quite nice to be able to point a Micropub client to a Micropub server, and have it render an editor for all the given post-types, with all the given properties, instead of needing to build the client with some awareness of what is required.