The fiber aspect is definitely a plus. Keeps you regular, etc...plus higher fiber diets have been linked to decreased risk of colon cancer (i believe...).

Another aspect is vitamins/minerals/phytochemicals...obviously, you're more than likely going to be getting enough vits/minerals if you're taking multivits and MRPs that are fortified...but phytochemicals are things like flavones (soy), elagic acid (raspberries), etc that have beneficial effects on your overall health. There's still debate over the actual efficacy of these phytochemicals, but i've seen some interesting info on it - enough to make me interested.