cwenisch,
I have a limbsaver recoil pad on my Rem 700 in 7mmmag. I bought the gun with a very hard thin rubber pad on it. When i shot it, it was not very pleasant on my shoulder. I installed the Limbsaver and it became very easy to shoot.
I now have one on my muzzleloader and a slip on for my 30-30 which my daughter shoots.
As far as percentage of reduction i have no idea. The recoil is the same but it doesn't hurt. All i can say is that it went from uncomfortable to comfortable