PID has been a super power in my career. I've used it to solve problems others couldn't even approach (it helps being the only EE in rooms full of CS people). I can claim to have made hundreds of thousands of dollars by just typing in the control loop from my undergraduate textbooks.
Likewise. I have made hundreds of thousands of dollars building entire embedded execution environments designed just to host and run a 25-line PID function .. its surprising just how valuable a well designed PID can be ..
Most recently, as a manager, I had someone on my team use it to control our memory usage in a garbage collector. I've used it to control temperatures in multiple pieces of high-end scientific equipment. I've used it consulting. It's not a stretch to say I have been a hero multiple times.
CS majors (I was EE) aren't generally taught PID, and I have milked my arcane knowledge. It's very profitable to type in the control loop, do some Ziegler-Nichols, and go home early.
EDIT Oh, I forgot the most recent time I've used PID was with the high-school robotics team I coach. We used PID for part of our robot. I didn't go too deep with the students, it's really just a P controller, but it solved the problem, and dramatically simplified the code.
