One thing which is often overlooked is the gearing that comes with a 4x4. One previous poster mentioned using the 4-Lo to get up on blocks. I have also used it for steep boat ramps and descending steep roads when loaded. In most cases, I am in conditions easily managed by a 2wd, but really appreciated using my gears to stay at 15mph on steep fire roads rather than my brakes.
As far as 4wd for traction, it pays off on snow, gravel, and even the dirt roads in the Midwest that turn to goo with any rain at all.