I bought this for my 2 middle-aged cats. I placed the pad on the platform of their scratching post. Since one of my cats only leaves the pad to eat and poop, I think the concensus is it works great.
Each side has a different temperature, and I first tried the lower temperature side. My cats didn't really go for it, so I turned it over and found they prefer the higher temperature. I can feel the heat coming off the thing, so I don't know what could be going on with those reviewers who say it doesn't warm up. Ours is nice and toasty all the time
The pad is inflexible, so do not expect to put it anywhere you would need it to bend. I leave it plugged in all the time--I don't see how you could possibly be expected to "unplug when not in use", as your pet is going to be the one who decides when to use it. Regardless, leaving it plugged in unattended has not been a problem for us. It has a nice removable cover, though there are no cleaning instructions with it so I'll have to take my chances tossing it into the wash on cold water, and see what happens.