Colonel Rickey classically ordered his drinks "sans sugar".
Ian Johnson
Just tried this and I'm completely bemused by the suggestions below that it's "too sweet". Not puckeringly dry, but make it as per the recipe and it's excellent, well-balanced and satisfying. If the chocolate bitters are omitted then I'm sure you'll get a sweeter concoction, but that's not the drink, is it?
They may be using underproof bourbon, a common mistake