Good stuff. There is also workaround.org's ISPmail tutorials : http://workaround.org/ispmail
And of course the tutorial for Debian Squeeze is not yet available.
Disclosure: I am the author of the book this link points to.
I don't believe I will be doing a Dovecot chapter anytime soon, for the reasons I stated at the beginning of http://gogs.info/books/debian-mail/chunked/courier.html
But, I must admit, I really like Dovecots Sieve filtering.
I do plan to publish the books Docbook sources on Github, hopefully someone who has more experience with Dovecot would be interested in contributing.