For what it is worth: I had an 2004 1 ton single Dodge, pulling a 42 foot 5th wheel toy hauler. I decided to go dually, and ended up giving the new 2008 Dodge Dually with Auto Transmission a try (all trucks described here are 8 foot beds). I thought the shift button would give me the control I wanted. I put 5000 miles on this truck, including a trip to Wyoming, and traded it in for another 2008 with the standard.

The Auto up shifts at poor times. Worse however, it doesn't down shift in a timely manner, even when using the manual button. The exhaust brake is less effective, because the torque converter kicks out at the best braking rpms. The delay for the down shift for the exhaust brake got me braking when a better response from the truck would have been good enough.

Furthermore, my driving behavior with a standard is much more fuel efficient. Going down the road both trucks are about the same mpg (the auto has a lock up). But, with my standard, I usually take advantage of long grades and coasting while approaching a slowdown area. This with better up shifts, I do get better mpg.

Much happier.