user, group, /var/log/mirrorbrain are created automatically now.

Logrotate snippet left.

I think that the Debian dovecot package could be serving as perfect example; it 
creates a group, a user, has the respective prerequires on "useradd" and stuff 
like that, and it also installs config files. It has a -common package that 
mirrorbrain could also have (more obvious than "mirrorbrain" for the common 
files, and probably closer to the Debian packaging policies).

http://packages.debian.org/lenny/dovecot-common

In the recently created Debian packages, there are a number of things missing:

- creation of user/group
- package /var/run/mirrorbrain and /var/log/mirrorbrain, owned by mirrorbrain user
- package logrotate snippet
- move config (examples) from mirrorbrain package to mod_mirrorbrain package
  (the latter concerns also the RPM packges)