Steering wheel controls mainly. Also display of certain info on the DIC. Also watched some videos where people had other miscellaneous issues...seems like one was the light not working on the heated steering wheel (although it did heat). A minor gremlin I admit, but makes you wonder what others there might be. I asked about some of the issues I'd heard about...but never really got an answer. I had started looking at the Gen 3, but was going to go with a Gen 4. The only real reason I was looking at a Gen 3 was that was where a link took me to and I didn't know there was a Gen 4 till I looked at the whole website.
I guess mainly what changed my mind is that I really just wanted to keep a stock look, but that is my personal preference.