i'd say for general shooting, the Exposure Bracketing and DOF Preview are not critical functions.
Exposure Bracketing - camera automatically take a few exposures of the same scene. eg -2, -1, 0, +1, +2 stops. useful when u dun trust the meter of intend to do things like HDR.
DOF Preview - stops the lens down to the aperture set for exposure so that u can preview the DOF. u see, to facilitate focusing, composition, when u view through the viewfinder, u always view through the biggest aperture (no matter what aperture u set). the moment u press the shutter release, the aperture is stopped down for the shot. if DOF control is so critical to u, u can always view it from the LCD and then compensate accordingly.
i dun even know if my camera has these 2 functions, cus i dun use them.