8d 7h 0m 0s
I completed the whole route (34 miles/56km) unsupported, North to South, in 6hrs55mins on Februrary 14th, 2014. I started at the Milford Sound ferry dock at 8:45am, and finished at the Te Anau Downs Ferry Port on the southern end at 3:40pm. I was unaccompanied; I had no support team or pacers, I carried all my gear with me and only filled up water at the huts.
You can read more about the details of my run on my blog here: borderlinedesigns.tumblr.com/post/78387708620/the-milford-track
I'm interested to see if anyone else has done this popular hike any faster.
Yeah there have been quite a few times faster than that, but not really the kiwi style to brag about them and post them anywhere. I believe John Campbell did it in just under 5:30 a while back. Runners go under 7 there pretty steadily just to make the boats.