Here at more onion we're hosting most of our client's sites ourselves. This means we are hosting lots of sites which share most of their modules (ie. our standard Drupal installation). Reproducible setups, fast builds, sharing-module code among many sites -- This is where our new build-tool called dbuild.py comes in.
It started out as yet another wrapper around
drush make and
drush site-install but became a fully fledged download-extract-patch-symlink tool in the end.