I've got stock 225 tires, so the automatic tranny with overdrive makes a great highway traveler out of the jeep. I'm usually below 2000 rpm with my 3.07 axle on the highway, and it's a relaxing ride.
Once you get outside of how the factory configured the machine with big tires and such, then all bets are off. That's when the "OD Off" toggle becomes really important.
Personally, I very rarely use the switch, and when I do it's usually at the "on" ramp with a need to merge quickly.