I just got back from a CT to CO road trip with our Sabre 36QBOK. I won't go into detail how much I love the engine/exhaust brake on my '12 F350 SRW 6.7m but suffice to say it is awesome. That said, I have desended long grades both ways, tow/haul w/ engine brake OR shifting manually +/-, both do the job well. Now the cool thing, we went up Pikes Peak ( no, without the 5ver ), I used 2nd and third gear manually most of the way up, and used the engine brake (tow/haul) on the way down. The only time I had to tap the brake was rolling into the hairpins and at the mandatory stop midway down, which BTW my rotor temp was only 161 degrees. I think a lot of that was coming to the stop for the check station. But the engine brake worked great desending the mountain nevertheless.
2013 Palomino Sabre 36 QBOK-7
2012 Ford F-350 SRW 6.7 CrewCab ShortBed
PullRite SuperSlide 18k IS Rails
2006 HarleyDavidson RoadKing Classic