Alright. So I've been scrolling alternatively softly and furiously on this this page for a good five minutes watching the really nice / subtle acceleration / weightedness happen. And asking, "how do you do this?!"
Then I click on his blog and the first post is how he does it.
http://www.everyday3d.com/blog/index.php/2014/08/18/smooth-scrolling-with-virtualscroll/
Happy insom is happy now.