The change seems to be limited to just certain sizes (perhaps from 1 to 3 or 1 to 4), and some types of creatures probably aren't affected (undead, constructs, whatever else).
W9 Quickness and Spell Quickness didn't stack together this February, when it was tested (by vfb at least); Kristoffer also took part in the discussion and disagreed with the tested results. It is easy to test, though. Start a test game with W9 pretender, give an unarmoured priest Boots of Quickness (to avoid encumberance effects on APs), enter a battle and cast bless.
In the above scenario, the AP stay at 2x the base.
EDIT:
here's the link
http://www.shrapnelcommunity.com/thr...&Number=579879