Not everything is without its drawbacks. You need to consider the energy usage. These systems pull the same amount of electricity equivalent to a hair dryer operating all day and all night. Since it is a self regulating cable, you will draw more electric when it is colder out. Depending on the length of cable, you can add $.50 to $2.50 in additional energy costs.
But there are ways to lower your energy costs with Heater Cap. The system doesn't need to be on when it is bitterly cold or if moisture isn't present. You can turn it off when there is no moisture present or in the forecast (that involves trusting the weatherman) or it is below 10 degree Fahrenheit and is too cold for ice and snow to melt on the roof.
A simpler way is to install some sort of sensor. A temperature / moisture sensor will turn the system on when it is needed. The sensors turn on when two conditions are met; ice melting temperature (not bitterly cold, but cold enough for snow) and moisture is present.
A properly installed system will melt the snow and ice on a continual basis eliminating hazards from falling ice and slipper walk ways. Heater Cap is the best solution for these problems.