One observation I made when taking the initial drink from a freshly opened bottle is that, more often than not, the scotch does not taste quite as good as subsequent tasting. The difference, though certainly noticeable, is hard to describe - perhaps a "sharp" taste to it, as well as a stronger alcohol presence.
Left to stand by itself, the flavors will tend to meld and improve after a while. Air, I believe, is the reason for this change in taste. When the seal of the bottle is broken, and the cork is removed, air enters though the mouth of the bottle and interact with the alcohol. This renewed interaction between air and liquor, combined with the natural evaporation of the alcohol, serves to alter the flavor of the drink.
As always, bottoms up my friend.