What's better than the aggression factor is the aggression frequency (AFq). A little math:
AF = (Bets + Raises) / Calls
AFq = (Bets + Raises) / (Bets + Raises + Checks + Calls + Folds)
Because the aggression frequency has more terms in the denominator, it converges faster. You get a larger sample size quicker. Secondly, a player with a very high AF might not call very much. But they also might still give up on a standard number of hands. So a player with a very high AF can still have a reasonable AFq. You see this most often with very good nitty players at medium stakes. They call very infrequently, and either give up completely on a pot, or are pounding away.
I know hold'em manager always had this stat as the default, not sure about poker tracker.