From my boss’s experience, most milk frothing systems are not as good as they say they are. If all you’re doing is a drink a day then it will probably work just fine for you, but if you’re hosting a party you may not like it. I have never used one.
I have how ever built one out of an old 1 group La San Marcco. I was able to push 2 bars of steam pressure (hoping to take it up to 3 bars someday) and it was able to steam a gallon of milk at a time. I have since then removed the group head and am currently thinking of removing the inner heat exchanger so I have more room for water and steam. It took some time and a few runs at it but I did heat up a 5 gallon bucket of cold water to 198F the goal is to do it in 4 tries, it currently takes 7 steamings to raise the temp!
Sorry for all the info, it’s my little project I have been working on!