I gave the exam two years ago and studied 2006-2007 decks..again since i am planning to retake, i did decks again, 2009-2010 version
I have read both thoroughly and it doesn't make a BIG difference..but there IS a difference...besides few questions added, mainly the questions have been reworded to "appear" more clinically oriented..I havent re-read the 2006-2007 version again since i got the new one, but i did skim through it to see major differences and i didn't find any.
SHORT: get the new one if money isn't a factor, and especially if you would be doing decks alone..If u are going to use supplemental sources with it like First Aid and Kaplan i think u should be fine with the old one too.
My 2cents