I enjoyed the movie and the music.
By coincidence I've had a few songs of his on my MP3 player, though never knew the significance of who he was.
IMHO, It seems that Sixto Rodriguez sounded too much like Bob Dylan, and also played around the same time. The powers that control the music & movie industries wouldn't allow the competition...(reminds me a bit of Shakespeare's Merchant of Venice) Which is why his albums were never allowed to sell in the U.S.
I was a little disappointed that they didn't delve into the way the music industry swindles small artists, however they found a way to showcase the horrors of Apartheid, over, and over. ...Not saying they should have left Apartheid out of the movie.
Just disappointed it was left so unbalanced.
Leaving the big question unanswered, "Where did the royalties go that the South Africans paid?"