Often times it is hard to understand what the characters are saying, there is much mumbling.
However, the actor portraying Muddy Waters steals the show, and is worth watching just for him.
The absolutely frightful Howlin' Wolf is a must see (although he looks like they may have painted his face for increased effect).
And Adrien Brody does a decent job of holding the story together, although his character is a bit flat.
Beyonce is a surprise, managing to display genuine talent as Etta James. All in all, a good movie, light entertainment, good to pass some time but probably mostly forgettable.