I just installed one on my PT1911. After seeing them, and hearing about them, I found some at a gun show for 50 cents a piece. I bought two (supposed to be good for 1000 rounds). While I didn't notice any felt recoil change (it's a heavy full-size gun and I already have a compensator on it for practice rounds), I know that it';s basically supposed to help the longevity of the internal parts by reducing "shock" on recoil. I figured - if it works, great. If not, I'm out a grand total of $1.
There is a noticeable lack of metal/metal contact when cycling the slide by hand...