Upgrades are wizard-based but are securely performed from the Administrator account.  MyProBB automatically locks down (goes into maintenance mode) upon upgrade availability to keep the forum secure.  Upgrades include complete database rollback functionality in the event of an upgrade failure scenario.  The upgrade wizard is also time-sensitive as many servers limit runtimes of PHP scripts to 30 seconds.  Thus very large forums can be upgraded successfully.  However, most forums complete the upgrade wizard in a matter of seconds.