David I'll definately grant that the application of these principles needs to fit the individual user and that as exposure is reduced there is less and less latitude at the shadow end of the scale.
One point I'm trying to make though is that normally I don't print clear to the toe. I don't think I'm odd in this respect either. Yes, a certain number of us shoot tight enough to the toe or long enough scale subjects that a small change in EI might really matter. It is obvious from my tests that I'm not in that group.
A second point that I want to make, and that Mark Crabtree also made above, is basically summed up in the old axiom "expose for the shadows and develop for the highlights"; development changes have very little effect on film sensitivity and shadow detail; it's almost all about the exposure when we are placing subject matter down close to the toe. Changing your development from 100 style to 200 style is about fitting the scene to the paper not getting more shadow detail.