My announcement the other day has resulted in a small amount of feedback already (through various channels), and a few extra repositories to be added. There was, however, enough feedback (and the manner of it unstructured enough) that I think it's time for a bit of a follow-up:

• If you have any ideas about future directions this should take, then thank you! Please file them as issues against the extrepo-data repository, using the wishlist tag (if appropriate).
• If you have a repository that you'd like to see added, awesome! Ideally you would just file a merge request; Vincent Bernat already did so, and I merged it this morning. If you can't figure out how to do so, then please file a bug with the information needed for the repository (deb URI, gpg key signing the repository, description of what type of software the repository contains, supported suites and components), and preferably also pointing to the gap in the documentation that makes it hard for you to understand, so I can improve
• One questioner asked why we don't put third-party repository metadata into .deb packages, and ship them that way. The reason for this is that the Debian archive doesn't change after release, which is the point where most external repositories would be updated for the new release. As such, while it might be useful to have something like that in certain cases (e.g., the (now-defunct) pkg-mozilla-archive-keyring package follows this scheme), it can't work in all cases. In contrast, extrepo is designed to be updateable after the release of a particular Debian suite.