I'm currently watching black butler as well... I've been meaning to do that for a while now...
I don't really have much problems with subs since I've gotten used to them... Nearly everything on tv is in English, we hardly have anything dubbed besides a few children's programs... It is helpful though for learning your English...
I've learned that if you watch lots of subbed things you learn to understand a bit of a language on a subconcious level and it takes less time to read the subs cause your brain kind of fills in the gaps on auto-pilot...
Then again, that could just be me... (I'm a person that learns languages from hearing them used, rather than from studying them... I wish it were that easy to learn my history, religion and society courses

That's also the main reason I watch anime, it helps me study my main course from university)
Just looked at the clock and realized it's past 2 am... I'm going to sleep for the night... Too late already... G'night!