Maybe this isn't very revolutionary 
But I just discovered some quirks and features of the door handle buttons on my new-ish GT. If the car is locked, one press opens the driver's side door. Another opens the passenger side door. Ok here's what I just "discovered". If unlocked, another press locks the doors. This is great because now I don't have to dig for the key in my pocket to lock the doors. It can just permanently stay there.
I haven't messed with the passenger door yet, but I assume that button does the same?

But I just discovered some quirks and features of the door handle buttons on my new-ish GT. If the car is locked, one press opens the driver's side door. Another opens the passenger side door. Ok here's what I just "discovered". If unlocked, another press locks the doors. This is great because now I don't have to dig for the key in my pocket to lock the doors. It can just permanently stay there.
I haven't messed with the passenger door yet, but I assume that button does the same?