I have one and I only use it for them cold frosty nites, when the shield tends to fog up. I believe I wired mine the 1st time just to a power wire and it didn't really have enough juice. If I was going slow it never worked, but once I put out some ummfff she worked. last winter I hooked it to my hi and low for the heated grips. Seemed to work alot better here.
In my opinion from the small amount of time I use mine over my sno-x helmet, it works ok. You can get them cheaper then 100 if you look around.