I've been part of this challenge since Aug. 1, without even knowing it existed :) When my husband and I saw we were at the last $100K (originally $300K in Sept. 2004), we decided to do everything possible to pay it off by Jan. 1, 2017.
Aug 1, 2015: $101,100
April 1, 2016: $64,669
So, $36,404 done in 8 months. Not quite on track, but we're hoping to pick up some steam once the warmer months roll in (living in Maine, heat is a big cost in winter--no AC in summer). Working some side hustles and attic purge sales to get a little extra for principal.