OS X 10.9 Mavericks subtle two-finger scrolling changes (on touchpad)
I arrived at this page because I also perceived a subtle change in the trackpad scrolling mechanics after upgrading to Mavericks.  It does indeed feel that medium-speed scrolling is slowed down a bit from before (10.7 in my case).  I don't have a machine running the older OS to test this on, though.  

Anyway, I turned up the scrolling speed to max in System Preferences > Accessibility > Mouse &amp; Trackpad and find the new mechanics tolerable on that setting.  This is maybe not the solution you are looking for but perhaps other readers will be content as I am with this fix.