Really good article on aperture effect on landscape shots

I thought this article was very interesting and although my DSLR (40D) isn’t full frame, I still think I can apply some of what it shows… (in a nutshell, don’t use f/4 for landscapes!):

http://www.gdanmitchell.com/2007/04/12/sharpness-and-aperture-selection-on-full-frame-dslrs