There was a significant change in 2012 (USB was added earlier as my 2011 LS had it). GM added a HDD based NAV head unit that is by far the best system I have used. It has 20G of storage for music, no annoying CD whine with NAV, pause live radio for 20 min, memorize new roads, and split screen NAV/Audio. They will not work in older models, and its my understanding that blue tooth is linked to the on star module. I HATE the wife's 2014 my link system in comparison.