It depends on what you set it to (/how thick the cage is). For very thick cages such as acrylics, it needs to get very hot to warm the interior of the cage sufficiently. With tubs you'd probably be okay, but it's still a good idea to ventilate the space between the tape and the floor (I put two strips of plywood on either side of cages I use heat tape with, lifting it up an inch or so from the ground).

Heat tape is great and much safer than UTHs, but be sure to have a good thermostat (Johnsons and Rancos are great), or you may end up with a fire on your hands. Also, for the actual tape, I personally recommend flexwatt. It's much cheaper and more reputable than other brands such as ZooMed.