I tried a bottle of Mr Beer Black Tower Porter last night and I found that it is a very good Porter beer.
I brewed this straight up with no additives and using the 2 packets of Mr. Beer provided with the refill kit. This is a winning brew and I do recommend it.
I have a second batch of Black Tower that I made later with Fermentis Safale S-04, which is a British yeast and should be be even more tasty.
It is important to know that the MB porter is good, since there a very few substitute porter kits in the no-boil all extract world. (Lots of stouts but few porters.)
Anyway, Mr Beer Black Tower is very good and is on my re-purchase list along with my other favorite: MB Englishman's Nut Brown Ale.