Also, webmail, calendaring are future features in this product. I wonder how critical are those for people setting up their own email.
I wonder the same. (: I would personally use the calendaring.
One of the goals of mox is to make it easy to host mail yourself instead of go to/stay at one of the few large providers. I think folks commonly use the calendaring that comes with their free email address. And it seems many people enjoy their webmail over locally installed mail clients.
I switched back to using Google Calendar as a backend. It would take a lot for me to try a switch again.