Just my opinion, but if you are contemplating it then you probably need/want it. I ordered mine with the 4.30 and couldn't be happier. Granted I only have 700 miles on it in 2 months the truck rides great.
For reference, my 2008 F250 with the 5 speed at 70 mph ran 2000 rpms with the 3.73's. This truck with the 6 speed at 70 mph runs just a hair under 2100. Not much of a difference at all. I am looking forward to pulling our 10k pound fifth wheel this spring.
Also no highway driving at all yet other than the 210 miles home from the dealer and the gauge sets at 11.7 mpg. The same as my 08 6.4 liter.