Well, ozone supposedly makes your water crystal clear (like your fish are swimming in air). Also, it supposedly increases the efficiency of your skimmer since it reacts with the various compounds in the water.
However, ozone supposedly can cause health hazards to both fish and humans if improperly dosed (but by what I've found so far, that is unlikely with the Ozonizers made for aquarium use). An overdose of ozone can wipe out entire tanks since it is a very strong oxidizing agent.
Check out this huge thread for more info:
http://reefcentral.com/forums/showth...5&pagenumber=1