The opinion on the best gears depends on the goal:
Off the line - go to lower gears (3.73, 4.10, etc...)
Fuel Mileage -go for higher gears (3.08, 3.31, etc..)
Compromise - 3.55's give a nice blend of both.
I run the 3:08's. I'm not a stoplight racer and I do a lot of freeway driving. I get 17mpg (long term average over 5 1/2 years) and regularly get 20+ on the freeway doing over 70 mph.
At higher speeds the gears start to wash out a bit as wind resistance becomes such a factor.