My partner used them for a while, but found she was gripping harder with her hands when I braked, and she couldn't always feel what I was doing. So she just took them off and placed her hands on my hips, then she could feel what my body was doing.
Now she justs places her hands at the side of my thighs. And I forget sometimes that she's there
Probably don't need to tell you but you have to accelerate and brake smoother when you have a pillion on the back.