Yes, I have used one before. That is the way that warships get their fresh water. Better quality than what you get in the town systems IMO. But, and it is a big but, the Navy's system wasn't cheap to install, run or maintain.
It turned sea water into fresh water, depending on the ship I was on, made the difference between having a good supply or limited supply. But this was more to do with storage of the water. Oliver Hazard Perry Class FFGs could only store 25 tonnes of water, with a crew of around 220 (during peak operations), whereas the Anzac Class FFH could store 40 tonnes with a max crew of 180. More storage, less people, less water stress.