I have had them, and they do work, but you must clean them every time you change the water. I didn’t realise this, and wondered why there was a horrible stale smell coming from it. It was a bit of a faff, as I liked to use mine overnight, so it meant disassembling it and scrubbing it out each day. I used an old toothbrush. I had one in my office too, when I was working, and it was only because they both ponged that I realised they were the problem ?
I changed the home one for a hot stone type. They are like saucers that you plug in. They heat to just warm, and you put oils directly onto them - no water involved.
I got mine from Aromatherapy Associates. It is not their fancy new one that needs to be used with their own oils, but a small dark blue/purple one that works with any oils. (AA oils are lovely though).