My roommate and I decided to go in on all four Mikkeller Barrel-Aged Black Hole beers, especially since Al's of Hampden was running a special on all four for $30.
The first beer sampled was the Black Hole aged in rum barrels. The aroma consists of chocolate, vanilla, and honey flavors with a great rum accent. The taste is a dry, biting flavor with oak and rum hitting on the sides of the mouth. As a spoiler, this was the best one of the four in my opinion, but really close to the Bourbon. I personally like rum better as a spirit, and I thought that it was really complimentary to the beer.
Of the four beers, the Whiskey barrel aged beer had least head. Most noticeably, the beer had a potent whisky and oak aroma that really covers the chocolate, vanilla, and honey present in other versions of the beer. Furthermore, the dry, smokey flavor overpowers the flavors in the beer and even has a dry and smokey finish. Of the four, this was the least favorite as the whisky and smoke took over the beer and made it really difficult to drink a whole (or half) glass.
The bourbon barrel aged Black Hole had a similar aroma to the rum, but I thought it was a little sweeter. There was a a little bit of smoke and oak in the taste with a good sweetness added, all while maintaining the dry chocolate finish. I would say the bourbon barrel aged Black Hole was just as good as the rum barrel aged beer, but I voted the rum aged beer slightly higher.
The final beer was the Black Hole aged in wine barrels. Most noticeably, this version sticks the most to the glass. I thought it has somewhat of a subdued aroma but the chocolate seeps through with a hint of grapes. The taste starts with chocolate and leaves a sour bite in the back of the mouth. Overall, the chocolate and grapes work well together, and leaves a nice dry finish similar to red wine.