Karel Zak started a fork of Mutt back in January to integrate features the upstream authors deemed too radical, and today released the first status update. So far implemented is native notmuch support (inspired by Sup) which adds fast search, tagging, and virtual folders from notmuch queries. Unlike the current hackish solutions, all of these are available as native mutt commands and can be used in your muttrc. Additionally, patches from Debian and other distributions will be integrated. Source is over at Github, and a few screenshots are on their wiki.