Update Rate of PID Loops

[Tom Line]

Is putting PID loops in the area of the code that runs faster really that beneficial? If I recall, the 'main' portion of the loop updates at 20 hz, or every 50 milliseconds.

I took a single signals class in college and while we touched on oversampling, antialiasing, etc we didn't really dig in. In this case, I look at our 150 pound robot and think to myself that 1/20 of a second response time should be more than good enough.

Is there something I'm missing? I'd love a whitepaper on this, since it seems to be one of the 'black arts' that we don't really talk about here, even though almost every team utilizes PID loops at one point or another.