In celebration of their tenth birthday, the Paramount Comedy Channel in the UK commissioned a study on how regional accents affect perceived funniness, and the conclusion was that people from Birmingham have the funniest accents. The Received Pronunciation, which is the only British accent most people in the United States are familiar with, came in dead last. I'm sure that there are some nuances of class that I miss out on when I watch a British-made film due to my lack of familiarity with the connotations that each accent brings to the table: Which accents are the aristocratic accents, the working-class accents, the stereotypical football fan accents, and so on.
I wouldn't be surprised if the advent of mass media has taken its toll on regional accents, softening the harsher edges and bringing them a little closer together. Which I think is kind of sad.
[Assorted typos fixed, 10:15am.]