Great advice. I used to use log4net in my database applications (now I just use my own custom logger). I have debug statements scattered throughout my code, and when I turn debug level "on," I collect performance information about my application.

From time to time, I turn debug level of my logger on, and re-collect my baseline. Then, if a problem arises related to performance, I can gather the current performance metrics, and compare to my baseline. Without it, you're shooting blind.