I bracket all the time when doing low-light photography, and whenever there's a lot of dynamic range in the scene - ie. deep shadows and bright highlights. As with shooting digital there's practically no cost in shooting three times as much due to bracketing, so go crazy.
Bracketing can be used for some advanced techniques. Google for digital blending and you'll get to a LL (and other sites') article on one of them. Another one is high dynamic range (HDR) imagery.
I think of metering like a rifle and bracketing like a shot gun.