If your cats aren't too bright, the mat always has to be in place. I was hoping my cats would learn to avoid certain areas so I can move the mat around, but have unfortunately had to buy an extra one along with an extension.
If you want to keep cats off certain furniture, this is a great product. If you want to train your cats to stay away from a place, it might not work, depending on how smart your cats are.
With my older mat I've noticed that the activity light goes on by itself and the mat shocks the air (I hear the noise) every once in a while when there is nothing on the mat. This wastes the battery (be aware that you have to buy a 9 volt battery separately, as it doesn't come with the product). Despite this, the battery seems to last a long time (almost 6 months).