The concept isn't bad but they seem to run small. The only ones I've ever had that would properly fit gloves were the built-in/removable covers in my Tourmaster Winter Elite gloves. Those gloves never leaked through on me, so maybe that's another glove to add to the waterproof list. I stopped wearing them when I went electric, because I much prefer riding in thinner, more flexible gloves.
I have a pair of the Tourmaster Winter Elite gloves. The outer rain cover actually works ok. It is good for about two to four hours in the rain and about one hour or two in a downpour. Then it is time to switch over to another so-called waterproof gloves.