You've got Keith's take on our project so far. Let me try to add a bit
of my own.
First, I like to call this project the "notmuch mail system" rather
than the "notmuch mail client". Our emacs client is just one (tiny)
piece of the system and I know that not everybody will want that,
(probably most people won't).
But a more interesting thing that Notmuch has is a really nice, clean
C library interface to all of the interesting pieces, (mail indexing,
fast search, tagging, etc.), thanks to Xapian of course.
So I would be quite happy if the developers of existing graphical
email clients took a look at Notmuch from the point of view of
integrating with the library for search. Personally, I've got about
600 thousand emails in my collection and I've yet to find a graphical
client which can search even a small fraction of that very quickly.
But with Notmuch, even the largest searches can return results almost
instantly, and that's really nice.
Then again, if nobody uses it but me, then I'll still be happy. :-)