1/1/10 no more retakes if you have already passed. You can have the lowest possible passing score and you will be stuck with it forever after 1/1/10.
1/1/12 exams will no longer be scored, they become P/F.
So from 2010 to 2012 you can still take the exam and get a score if its your first attempt. Whatever score you get, you're stuck with.
This is the according to the ADA. You may want to read the forums before asking a questions that's been asked NUMEROUS times.