Eddie,
A lot of the 3.6-3.7 delta is due to primitives broken or disused during the i8n effort. These include basic font printing and text layout. (Try editing a big paragraph in a workspace, its not pleasant) These issues have been reported and hopefully will be improved for 3.9.
I put a comment on http://bugs.impara.de/view.php?id=1650, but I think that the "editing a big paragraph" issue may be related to more the process scheduling than the failing primitives.
-- Yoshiki