What's the need for a temperature controlled soldering iron?
You always need a temperature controlled soldering iron. It's one of the first must-haves for the EE, together with a good DMM. Uncontrolled irons heat up to high temperatures while they sit in their holder, so that your first solderings occur at way too high temperatures, which leads to poor quality soldering connections and possible damage to (smaller) components.  



When in college we had labs where we soldered, but we were never formally taught how to do it. Many inexperienced hobbyists apply the solder to the soldering iron. Wrong! You heat up the PCB pad/ component's pin with the iron, and apply the solder to the heated surface. Only that way the flux can do its cleaning job on the surfaces.