Have you ever wondered how people plan for the capacity of a system? This presentation tries to explain how to do it. It is definitely an art, but the tools used here will help you learn how to do it with logic and reason rather than hopeful optimism. That should help you keep from under or over sizing the systems you build in the future.
The guys over at Phoronix reminded me that X11 turns 25 today. That's pretty awesome news. X11 has been the basis for Windowing on Linux since windowing began there. Many have tried to replace it but so for no one has. It's modular focus has let it last this long and makes it really hard to supplant.
Let us know what your worst X11 configuration nightmare was?