I have never tried Old Grand Dad in the past, nor am I a Bourbon drinker, so I don't have much of a reference. In any case I tried it with a friend and the first and lasting impression was that of an acidic taste. It's drinkable, but it seems long past it's time. In comparision to tasting notes that I have found for this bottle, it has only limited similarily to the expected "flavors of dark candy corn, non-tannic wood, and some light smoke, with a gingerbread-like backdrop" described in another forum.
I think I deserve a fresh bottle.