I've been wanting a scrubber from Harry's for a while, but this one is disappointing. My experience is similar to other reviewers. The body scrubber does not lather well and the scalp scrubber hurts.
Nothing more to say on the scalp scrubber, it's painful to use so I don't use it.
On the body scrubber side, I have another silicone scrubber that lathers very well and I see 2 main design differences: the length of the bristles, and the base of the scrubber where the bristles attach. The bristles on the other scrubber are 1/4" and they attach to the base of the scrubber where it makes direct contact with your skin. So the body wash is actively getting lathered when you scrub.
The bristles on the Harry's scrubber are 3/4" and they attach to a base that is not flush when you scrub it on your skin. There's this middle perimeter that divides the two sides of the scrubber, it's the part where you grip the scrubber to use it. The design of this perimeter creates a dip, like a spoon rest, where the bottom is lower than the rim. So the parts that makes direct contact with your skin when you scrub are the tips of the bristles and the rim of the perimeter, instead of the full surface area of the base of the scrubber.
I think the Harry's scrubber needs a redesign to be useful and feel good to use.