In listening to American distillers and brewers, one gets a sense that the yeast used to ferment sugars into alcohol is important to the process of creating flavorful whiskeys. The best example I can give off the top of my head is Four Roses Bourbon, which employs at least 5 different types of yeast in creating its 10 different recipes for bourbons. Having done a tasting of the full flight of all 10, I found I was partial to the bourbons made with lower rye percentages in the mash that were fermented with the more floral strain of yeast.