kg4wsv:
Around here (university engineering department that teaches controls) the consensus seems to be that PID is less effective than other control algorithms, but it is used because it is simpler (to implement and understand).
PID can be applied to a wide variety of systems, and is conceptually simple. What 'other control algorithms' are you thinking of? The P, I and D elements each have a distinct purpose and are each simple to understand. P alone and P+I each represents subsets of the full PID which might work OK in specific situations, but if you omit the Integral term it may not converge on zero error, and if you omit the Derivative term it is liable to suffer from oscillations.