I use them and have not had any problems, but if you opt for "safer" routes there are heat panels, heat tape, and other sources of heat. If you go with and of the panels or tape be sure to hook it up to a rheostat. If you use the human heat pad brace the tank up so there is approx 1/2" gap between the pad and the tank for air flow.
As for the temps.....
85-88° on the hot side of the tank for day time MAX!!!!! (95° will roast your snake!) Allow a 5-7° degree temp drop at night.
1.1 Columbian BCI, 1.2 Hog Island BCI, 1.0 Irian Jaya Carpet Python, 0.1 Ball Python, 0.1 Children's Python, 1.1 Amazon Tree Boa, 1.1 Dumerils Boa, 1.0 Horned Mntn Dragon, 1.0 Carolina Anole