I put one on my 870 and it is simply amazing.
I took it to the range for the first time this past sunday and put 30 rounds of various types of shot through it. Little or no felt recoil. Slugs kicked the hardest, but even then I could have spent all day shooting them. The only problem I had was that my arms were getting tired holding the gun up! (Note to self: Do more push-ups).
It was really easy to install and worked as advertised. Money well spent.