A lot of folks like them. I had one on a Browning BT-99 Golden Clays a few years back, and I never could shoot it. Nothing against Gracoil or the quality of their stuff. I've never seen a negative comment about Gracoil's quality.
The problem I had with it is that I tend to pull the gun in as I shoot, which changes the length of pull, even with the spring cranked all the way down. That changes your point of aim. I ended up selling mine after of few months of frustration. The new owner had no problem with it, so it's probably just the way I shoot.
I'm probably a minority opinion here, but I would suggest shooting one before you decide. It's a permanent change to your stock, as I recall, so it's not something you can undo.