Code never lies, comments sometimes do.
Simple, not easy. There's a difference.
One of the great skills in using any language is knowing what not to use, what not to say. There's that simplicity thing again.
It seems to me to be important to distinguish a good idea from poor implementations of it
If there's only one answer, then this must not be a very interesting topic.
The lesson is: Even if you know exactly what is going on in you system, measure performance, don't speculate. You'll learn something, and nine times out of ten, it won't be that you were right!!