Have used the SIG P226 and Glock 19 (Gen 3) version of this spring system.
The SIG P226 worked perfectly, but didn't seem to change recoil significantly.
The Glock 19 version also worked without any failures, but was much more noticeable in its recoil reduction, almost equaling the reduced recoil of the Gen 4 Glock 19.
I think it depends on which pistol you have and how much recoil there is as a result of the basic design. On a polymer framed Glock, the reduction was significant. On the SIG, which is a pretty smooth-shooting pistol anyway, not so noticeable for me.