MuddFlapp, '06 and '07 have the full electronics package, engine control and transmission control to do all combinations of exhaust brake, tow haul, all with cruise and the button also can lock out OD as additional function.
'05 and older 3rd gens all have some hybrid combo but out of the box can't do torque conv lock w/exhaust brake & cruise.
I'm drop dead in love with both my rigs.
'07 sits 9 months, drives 3 mo for 10k or so. I'm going to install one of the fuel heaters to cycle engine water or oil as it sits for the 9 mo, otherwise I drive it once a month for hour or so.
Sounds to me like the hard working 6. 7's do ok.
I'm mostly urban driver in Puget Sound with my '06 and have couple key hills where drop into 4wd go full throttle 3-5 seconds or so. At 9k miles the '06 has been loosening up considerably last thousand miles or so, hopefully the horsepower pulls help out.
See you, Jim.