OPS is simply a way of looking at how good a hitter a player is in a total sense. By looking at the parts, you can see what type of hitter a player is: High OBP, low SLG = gets on base well but doesn't hit for a lot of power. Theriot is a good example right now. Low OBP, High SLG = player hits for power, but probably is not too patient, see Soriano. High OBP, High SLG = Well rounded player. Low OBP, Low SLG = sucks.