Put 50 rounds through the other day while we were at the range. To me, it seemed like there was more felt recoil, but it was more controllable. The new grips are just a little bigger, a little grippier, and the finger groove all do a much better job of keeping the gun firmly planted where it belongs.
Also, despite the grips being more efficient at transferring the recoil energy, my hands still felt better than they did after the 40 rounds a few days before with the factory rubber.
These are definitely worth looking into if you have a J-frame.