First time diesel owner (2021 Duramax 3500) but have been traveling back and forth between NE Wyoming and Arizona frequently the past few months (already at 8k miles). I can say that when running cruise with the EB off the truck doesn't hold it's speed at all on the downhill grades (set at 65 hitting 75 within a mile it seems), turning on the EB during those long downhills the speed stay's locked at whatever I put it with no variance.
Only towed the rig (14k 5th wheel) a short distance so far so I can't speak to it's effectiveness, but it does seem to work well in my opinion traveling around Window Rock and Santa Fe.
