hg.mozilla.org is imported as needed by the ETL processes. It would be nice to have a daemon fill in all the other revisions so users can query the repo fast.
The repo will be useful when regressions are found. dzAlerts suffered from lack of "repo analysis": Meaning dzAlerts did not look into the repository to find the list of changesets that possibly contributed to a regression; the list of changesets between a known "good" state and known "bad" state. The alternative, in the case of dzAlerts, was to simply blame the canonical changeset of a push. Having the system place bounds on its uncertainty will make it trustworthy, and provide information about what changesets require more testing in order to reduce that uncertainty.