Acid cleaners are great for urine, for hard water deposits, for soap scum all of which can be found in bathrooms.
Ideally use an alkaline cleaner first (Viper Venom or the new PeroxiBlast), followed by a cleaning with acid (Viper Renew or the new Peroxibright). Then neutralize or rinse well. Leaving the grout with acid on it will gradually deteriorate the grout.