I have met several that have.
The two that got the one made by Girard were not happy with them.
You turn the cold water off at the faucet and regulate the temperature by adjusting the flow rate of the hot water tap. In places with low water pressure they didn't get much of a shower.
The three that bought the one made by Precision were happy with them. They regulate the temp by a thermostat that adjusts the flame.
Clay WA5NMR - Ex Snowbird - 1 year, Ex Full timer for 11 years - 2004 Winnebago Sightseer 35N Workhorse chassis. Honda Accord toad.