The major problem with the email-patches workflow is that it is a pretty poor experience for the new and occasional contributor, who will generally find that their email client makes a complete pig's ear of their patch. What I'd really like to see is a web UI that seamlessly interacted with the trad email workflow, so people who prefer a web UI and especially people who are just making a single drive-by contribution could work that way without having to start by setting up git-send-email. You could also make the web interface keep track of which patches are still unreviewed so things drop through the cracks less often...