Excellent cake! I made it for a Valentines day treat. I didn't have dark rum, so I used light. Also I had semi-sweet chips, so I used those instead of unsweetened.
It came out great! I also invented a fabulous glaze for it after looking in my cupboards: to one cup of powdered sugar add 1/2 t imitation maple extract (gives it a great caramel color), 1 t. rum, and enough cream to give it the desired consistency. It's so sinfully good!
Very rich, but not too sweet. A big hit the two times I made it. I definately needs to cool completely before you turn over the bundt pan. It's so moist it will come apart if it's not cool. We put the pieces back, topped the whole thing off with a chocolate ganache and went to the party!