I had the Vacu-flush in my last coach and now in my HR. They are popular in coaches built by Allied with 2 toilets. Although they are designed to flush with less water, mine seems quieter with more water in the bowl.
You can leave the switch on all the time if you wish because the vacuum cycles the motor off. My systems have been reliable, no problems. Because they use so little water, its possible to get 25% more flushes between dumps. Also the vacuum moves the waste very fast to the tank and the velocity breaks it up eliminating the pyramid so its easy to empty.