Most of the time your time is better spent adding feature to an application then trying to tune performance in the ways he talks about on the site. Most of the time it is easier to scale across multiple machines and pay for the hardware then it is to put in the time to make a program this efficient.

But there are applications like Snort (which he seems to reference a lot) that can't be split onto multiple boxes easily, so tuning for max performance is very important and is a key feature of the application.