Nice post. I pretty much know all of this stuff, but don't practice it often enough! Reading someone else's take on the subject always adds at least some nuance and I am once again inspired to drop out of Program mode (yes, my default).

On my Pentax camera, there is no 'S' mode. It's called "Tv" and Aperture priority mode is called "Av". They respectively stand for "Time value" and "Aperture value" which, if you think about it, is slightly more descriptive of what you're doing.

Also, the 18% grey fact is, apparently, not a fact. It doesn't alter your advice at all, but last time I published that figure I was pointed to this: http://www.bythom.com/graycards.htm

Finally, some time ago I published a summary of a forum discussion resulting from my exposure problems with my first DSLR. It contains a lot of great observations and advice and I thought it might be of value to your readers. (It was here the 18% grey thing came up.) You can find it here: http://www.sittingduck.co.nz/pmwiki.php/Photo/DSLRExposure