Probably technically I'm not as skilled as everyone else, but I seem to recall with "good old film" camera (Canon AE1) how often I missed those "special shots" because of the time needed to focus manually to make sure that the fleeting expression was sharp! Plus the time needed to push the lever wind.
I have a Nikon F70 - that's terribly slow to operate on auto-focus and can hunt really badly.
I also have a Canon 28-90 film compact. It's slow to focus too!
Yet my "elderly" Nikon 995 - if pre-focussed - is pretty well instanteous!
Since I've acquired a D100, the speed of focusing and taking is so fast I've missed far fewer shots and I've enjoyed my photography far more.
As for planning and experimenting, I couldn't afford in the past to waste film etc on too much playing with ideas. With a digital camera I can be much bolder, I think I'm getting better results - and there's no cost due to wasting film!
Howard