I've been using them for the past year. Except we use a combination of different size and shape pinches and blocks in a pinch workout.
Start with the 2.5" spheres.
Move to the 3.5" spheres.
We have 3.5" hemispheres fixed on the Campus board at the same intervals as the rungs. ( actually 3/4-spheres rather than 1/2).
On to a 4" tapered block for a few asymmetric pulls/hangs.
And a couple sets of repeaters on the BM 45's.
Then finish on the "tufa" pinch hold...
And some guys use the various sized pinch blocks and free weights, we've made up for the purpose.
If you're an animal, there are 3.5" spherical pegs for the peg board, but that just fucking hurts.
And it definitely helps improve your ability to hang a Sloper or a pinch.
The 3.5's are damn difficult to hold properly. Most people start by holding them with the palm partway up the side (almost as if it were a vertical pole) and work up to the full, base of sphere in palm, hang.
If you're holding the spheres with the chain/hanger between the front two or between front and back two, it's a waste of time.
We have a workshop upstairs at the Bunker and the boys spend far too much time shaping bits of wood, very scientifically, into something that "feels" right...