I agree completely - it is just personal preference, but if the shot "needs" the sky replaced, then I just didn't do my job properly. If I can't get back to that locale to re-do my shot, then I live with it as is and remember the experience.
This statement is soo true!
The adjustments that Adams made took a great deal of skill (and money) in the darkroom and were part of the artistic endeavor. Adjustments in PhotoShop just don't compare on that level.
I may have just shot myself in the foot or started a riot - apologies if I have irritated or offended anyone - but that is how I feel.