I wouldn't go so far as to say Flexwatt is "junk" but, I am very happy with my THG heat tape.
It does seem consistent but, mine is less than a year old and it seems pretty durable if you are using it in rack applications.
The big selling point for me was other users had found that if you use the same length/# of elements that the THG did not require rheostats or potentiometers for each strip to maintain each tub at the same temp's. That consistency of manufacture indicates either a better manufacturing process or better quality control.