Sarah, thanks so much for the shout out to GitHub Updater. I can honestly say that developing on GitHub has made me better and made eat his plugin better. I couldn't have done it myself and I've had lots of help from the ubiquitous Gary Jones and Seth Carstens.

There are reasons it wasn't allowed in the WP repo and it mostly has to do with promoting an outside repository. As you pointed out, there is no code review or the ability to pull a plugin/theme out of the repo on GitHub. In the end I believe the WP repo maintainers were just looking for the safest experience for the majority of users.

Thanks again for the shout out.