Delicious! Sweet and velvety, but not cloying. Based on Simon Sedgley's suggestion, I may try substituting Hogsworth (a craft blend of bourbons and aged armagnacs marketed here in the US) for the armagnac the next time I mix one. Will add another comment if I do.
So, I finally did try it with Hogsworth substituted for the Armagnac, and I liked it even better! I also tried substituting Cognac for Armagnac, and that was good too. (Hogsworth is a 60%/40% blend of bourbon to Armagnac, so if you can't get your hands on any, blend some yourself!)