Grain is often identified as the base of a great Bourbon's flavor. I wonder, however, to what degree the yeast used in the initial ferment plays in the process. As I've learned in my experiences as a homebrewer, the variety of brewer's yeast that one uses has a delicate, but very noticable effect on a beer's final flavor. Any thoughts on this? I would guess that the rather "rough" process of distillation kills many of the more subtle notes left behind in early fermentation, but this is all speculation on my part.
On an unrelated note, I would suggest that anyone interested in the process of making whisky learn how to make all grain beer at home. I have toured the distilleries before and after I became interested in brewing beer at home. Knowing a little more of the technical end of things really adds to one's appreciation of the difficulties in distilling Bourbon.