Does mail-in-a-box then provide the scripts to perform regular software updates and any configuration migrations between versions? There's more to running software than the initial setup... A complete Mail solution in a Unix-like environment consists of a lot of disconnected programs with their own configurations that are difficult to get running, and even more difficult to maintain without a full time systems administrator in place.

If so, I'd be extremely tempted to switch over. I already use Postfix/Dovecot/Roundcube, but Roundcube is currently broken because of conf changes between upgrades and Dovecot has been _horribly_ broken (taken a week+ to sort out) by a big configuration change on their side a couple of years ago :\