I used a heat lamp AND the UTH in the winter, only because my house was so cold my snake would had to have spent all his time under the aspen to keep his body warm. The air in his cage would have been about 70 without it. I used the heat lamp (it was one of those red heat-emitting bulbs) to warm the air in the tank up to 80. The thermostat probe sits on the glass over the UTH pad, so it would make sure the tank glass would never get above 84-85 or so. With the heat lamp on the same side of the tank as the UTH, he still had a warm/cool gradient.
Now that it's summer I have taken the heat lamp down and only rely on the UTH and it's perfect. I wish I didn't have to use the lamp in the winter because I like the natural light much more.