I'm in the 80/20 gang, had great results with it. I have to say, often it is not emphasized that besides building the aerob base (my average HR went down significantly) it also helps avoiding injuries. Simply because you get used to be on your feet for a long time and you don't surprise your body with unexpected trauma. I was surprised that despite running at my goal pace rarely, I was able to do it on race day with relative ease. (I'm talking about half marathons for reference)