I did an out-and-back ride of about 15 miles in July of 2005. I started at the campground and missed a turn and ended up heading back to Medora. Heading back to Medora was mostly downhill it seemed.
You can access this trail by riding out to the western exit of Medora under I-94 or you can get on it at the Buffalo Gap Campground which is about 6 miles west of Medora and it starts right at the day-use parking lot.
http://www.singletracks.com/item.php?c=1&i=1783