you know what the hardest part of Henninger is? if you enter/exit from the gated area and don't come up Eaton Canyon, it's going up that last little hill just past the bridge. freakin' brutal.
I actually find that part relatively okay, since it's at the beginning of the run (it is a steep part though). The worst part for me is the turn into the "canyon" just past 1.5 mile mark. It's short, but goes from a relatively flat part to a super hard climb, and is far enough into the run that it really has the potential to kick your ass. More than once, I've had to pause to catch my breath either on that part, or right after it (before the 2 mile mark).