Machines and processes are controlled using ... This temperature swing (error) around the set point is not accurate enough in many industrial control processes. To reduce the process variable error, ...

[Harvs] hacked a cheap PID controller ... a DS18B20 temperature sensor. At the lower temperature ranges [Harvs] is interested in the DS18B20 is far more accurate and easy to use than the thermocouple.

Not only are they potentially unsafe (mainly because of the inadequate stand they come with) they can be hard to use, slow to heat up, and you never know what temperature you are soldering at.