Based off of recent posts I think a lot would have to do with driving style. I have 2012 5.0 with 6 speed. I don't mind the transmission but would probably like the 10 speed, I'm always trying to be in 6th gear on any back road or highway, only want to use the lower gears when needed, I'm not racing anybody and if I need to pass time to downshift doesn't make a difference, I'm not shooting gaps between cars on the freeway.
I do appreciate the closer gear spacing and not having the big jumps in RPMs that old 4 speeds had. I'd be hard pressed to go back to a 4 speed for daily driving duties, would prefer to move up to the 10 speed. Building a race car is another topic though.