Oh, I've the same feeling concerning British. Australian and Black American are ok. But what about South African English? It sounds like German! And you still can understand it. The only "English" I totally don't understand is Jamaican!!! Of course, it's the hybrid of English and some native (local) Jamaican language, but Jamaicans still call it "Broken English". By the way none of my co-workers are able to understand it too. So seems to be we need to find the definition of where the English ends and something different (hybrid in this case) begins.
I?ve had some difficulties trying to understand Indians, especially the way they speak with each other mixing English words with Hindu or whatever language they speak. Once there was a funny situation when I said to my friend in Russian that we had to buy a watermelon. An Indian guy was in the same room and started laughing when he heard the word ?арбуз?. It turned out that in Hindu they say ?garbuz?, so we found at least one common word that Indians and Russians use. Now I wonder where the word garbuz/арбуз comes from.