Is it a significant issue that the Rocket Appartamento does not have a PID for temperature control?
The Rocket Appartamento is a heat exchanger espresso machine. Due to the way a heat exchanger is designed the PID does not have as much benefit as if it were on a double boiler or a single boiler. The PID on a heat exchanger machine is similar to having a pressure stat. It controls the temperature of the boiler which, on a heat exchanger, the boiler is kept at steam temperature. So when you're adjusting the temperature on a heat exchanger through the PID you're adjusting the temperature of the steam boiler. This raises or lowers the temperature of the steam boiler which indirectly raises or lowers the temperature at which you brew. So in answer to the question, there is a benefit of having a PID on a heat exchanger but it's simply to just provide an easier way of raising and lowering the boiler temperature versus precise brew temperature.