Aggression Factor

[ajmargarine]

Being new to Pokertracker, I'm still getting a feel for the ins and outs. Of the basic stats, I understand VPIP and PFR% and what is the norm and what is crazy in those numbers.

But, I'm still trying to "get" Aggression Factor. First off, when people provide this number in a hand thread, are they including preflop in the equation? My numbers for NL100 full are:

1.07 (with preflop included)
2.73 (without preflop)

I understand how they get the number...but...how do these numbers compare to yours? What are good parameters that you have found where you can say this guy is crazy aggressive, and this guy is way passive? Thoughts on AF are appreciated for this newbie.