I used to have one in a Series 80, and went many thousands of rounds with it. They really don't increase accuracy in my experience, but they do cure pistols that shoot a decent group one minute, then throw a shotgun cluster the next.
I have used one and I do not recommend them. While they do work, they do have their own issues. First, they do require some fitting to get the link in the right position for the spring to act on properly. Second the leaf spring being part of the spring guide tends to dig into the link over time, which means that links need to be replaced.
If you are considering a group gripper, I would suggest that you do two things instead. First, have a gunsmith check and replace the link in your barrel with one that is the proper size for your pistol if necessary. Second, install an oversize bushing and a full length guide rod. The bushing will hold the muzzle of the barrel in the proper position, and the guide rod will support the recoil spring on its full length and will make the slide action more consistent, which will make your pistols mechanical accuracy more consistent. In addition, the guide rod will counteract some of the torque in the barrel caused by the bullet passing through it, which also helps the pistol's mechanical accuracy to be more consistent.
My first 1911, a Colt "Enhanced Model" had loose lock up. The group gripper with the addition of a NM barrel bushing made the gun a 1.5 shooter at 25 yards. I put around 52,000 rounds through that gun before I sold it. It never had an issue period.
I guess I should have given more info, I am a machinist and do all my own gunsmithing, I have installed a longer link and heavier spring to help lock up whitch has helped improve it's grouping, but the main problem is that short of replacing Colts poorly fitted barrel I have done all I can and was looking for an option since I really don't want to buy a new barrel and bushing right now.
I put one in my Combat Elite over ten years ago. It has helped the accuracy nicely and I have had no relibility issues with the gun after many thousands of rounds. I'm sure that having the barrel fit to the slide by a quality smith would achieve the same effect, but for a "quick fix" it has served me well with no negitive issues.