I have the Apex Duty/Carry enhancement kits in all 3 of my M&P's, a .45, a .40, and a .40C, and they are a definite improvement. Add a Wolff 4 Lb. striker spring along with the apex kit and you will be amazed at the difference.
TIP: Keep the factory trigger spring instead of installing the Apex for an even lighter pull.
I just got the Apex kit and trigger installed in my shield. for anyone contemplating this, DO IT. it's like BUTTA now. I can't wait to get it back to the range. the only issues during install were self-inflicted when I got reassembly out of order. went back and rewatched their video, did it in the correct order, and then it went back together like it should.