But it's use really depends on your ambient temperatures. Also keep in mind that the enclosure will still need lighting. You could certainly experiment with it, but I can't go without heat lamps because of my house temperatures. In the summer my main reptile room tends to get too hot and I end up switching some lights off and such, but in the winter my ambient room temperature stays around 68f, so reptiles that I used a heat pad for in the summer (my ball python and my leopard gecko) now need red heat lamps to keep ambient temperatures where they should be.
My female russian torts definately need heat lamps. For one, their substrate is about 14" deep, but also in the winter their room (in the basement) gets as low as 60f, sometimes into the 50's. For that I use a red heat lamp that stays on all of the time, and then several other basking lights that turn off at night (it's a very large enclosure). I also have almost no ventilation on that enclosure, because otherwise the heat would escape all of the time. I already have enough trouble with heat escaping when I open the top to feed them.
You might want to experiment with it, but I personally would use it in conjunction with a heat lamp (but a lower wattage would probably work). You might try what I do for my ball python. Put both the pad and the heat lamp on the same dimmer, so then when you set the temperatures they will be working in conjunction with one another.
I was concidering getting a pig blanket for the russian tort enclosure, but I don't trust those enough to put them inside of the enclosure.