I know that many people might want to learn Northern Vietnamese since that is what is primarily used on TV (as well as spoken in the North) and I personally have nothing against that particular variety of Vietnamese that, but I'm casting my vote for additional audio content with Southern Vietnamese since most of what I hear is from the South. I wouldn't be opposed to hearing some Vietnamese from Central Vietnam, too, as long as it's clearly identified as such.
Thanks for the great lessons and I can't wait to see what's coming up this year.