Quite nice, 4+/5. The only vice is that it is rather sweet (but not cloyingly so, and the richness works with the dark/burnt molasses.) Jamaican rums and other dark rums can be sweeter-than-optimal in cocktails that lack balancing citrus acidity. I ordered the Cruzan just to try this recipe, and was pleasantly surprised by the rum's balance of the darker/bitter molasses, alcohol heat, and the sugar level, it really works for me. Lemonhart 151 is so much drier, harsher by comparison, likely because it has nearly twice the proof. To reduce sweetness of the drink, one could replace the the Smith & Cross, and a portion of the Cruzan with a gold rum.