Hey Bilbz, I use one and have done for a couple of years.
My car doesn't have the facility to use a key except in an emergency and then it is a pain in the area to get everything back to normal.
Mine is a SURFLOC. It works fine for what I need. Though I don't live in a city or where vehicle break ins or thefts are common.
I just put my electronic key in there lock her up and I lock it to the tow bar hitch. Haven't had a problem with it. Even if it is raining.
ET.