I'm a long-time nmh user, and I heard notmuch was supposed to handle mh folders, so I gave it a shot.
It's crazy slow. The first 'notmuch new' took 4 hours, but maybe that's expected. However, every 'notmuch new' takes 4 - 10 hours. The only time it completes faster is if I immediately re-run it without incorporating new mail. In that case, it completes in 0.8s - 38s, which is quite reasonable for my mail. I have 18.5 GB, 1,058,370 messages in 315 directories.
