Can give you the flexibility of a double boiler machine withour the expense
Positive Product Points
Provides a good alternative for immediatly steaming milk. You can have the functionality of a double boiler machine without the expense
Negative Product Points
You cannot just leave this on the stove as the water will boil away over 15-30 minutes. I use a gas stove and am not sur if it will work so nicely on electric... it may but I have no experience.
I bought this unit used some long time ago. I just thought it would be interesting to have it.
Eventually, I settled into making cappuccinos for myself and my wife. Since I have a single boiler machine, there is a wait as the machine heats up to steaming temperature. I did not like that wait and so I started using this stove top steamer that I had sitting around.
Now I use this exclusively to steam milk. This arrangement lets me steam immediately after making the espresso... sometimes even while I am pulling the final shot.
Another thing that prompted me to begin using this arrangement was that I once took apart my old Gaggia. I was really shocked to see how much mineral build up there was in the boiler. I figured that I could reduce the tendency for build up by using this stove top steamer. And in fact, I noticed mineral build up in the steamer as well, Of course this was much easier to remove than build up in the machine boiler.
Of course, eventually, I installed an in-line waterde-mineralizer. But I am never sure if maybe they stop working before I recharged it with the salt bath. Now, I use reverse osmosis water, so the mineral content is not an issue.
But still, I like having immediate access to steaming, so I continue to use this unit.
Note-- the unit I have is different from the picture that you see. Mine is an older unit that is full chromed steel with a knob valve for the steam wand. I am not sure how these units pictured work... but I assume they work as well.