So far I have enjoyed the D4. It is easy to use, I feel safe climbing with it, and is built with a quality feel. I use it with a micro pulley attached to a hand ascender above and a foot loop attached to another hand ascender below. I can add a foot ascender below also for variety.
The D4 works easily both ascending and descending and has no-brainer safety features built in for the descent. Since the gripper cam engages immediately with any downward force no ascending progress is lost (I advance, sit, advance, sit, etc). The narrow threshold of lever travel before tripping the gripping cam on the way down takes some getting used to but a few practice runs will be beneficial.
One other down side (if it is that at all) is the D4 is heavy. If I were needing to trek 10 miles to get to a good tree I might leave the D4 in the truck and use another climbing system. Fortunately we have lots of good trees in East Texas that are a close walk from your vehicle.
Overall I am well pleased with the D4 so far and will use it frequently in my climbing. Thanks ISC.
Reviewed by: Peter Austin from East Texas.