This is definitely not a recommendation to go out and buy or use this tool. I am recommending that you allow an experienced luthier use the Bridge Saver to repair a badly damaged bridge reinforcing plate. This is the thin 2 inch x 4 inch hardwood plate glued to the top under the bridge. The string ball ends pass through, rest on, and exert considerable pressure on this plate. Most of the sound quality of your acoustic guitar depends on this plate. If the string holes are enlarged or damaged and if the ball ends are pulling up into the plate, the guitar is likely to suffer serious damage, not to mention reduction in sound quality.
Frank Ford's repair people also recommend this tool.
The hard part of the repair is cutting and fitting the matching plugs, one for each hole. (I suggest operating on all six string holes.) For best quality sound, I recommend using fresh mixed, hot hide glue (from powder) and Brazilian Rosewood plugs. On most instruments, this repair causes some improvement in sound quality. On a few instruments, the improvement is dramatic.
There is no evidence pro or con as to the longevity of this repair. The tool -- and therefore the repair technique -- simply has not been around that long. We may find that plugged bridge plates crack or deform in twenty years. However, the bridge will certainly fail if the reinforcing plate is not repaired. Since removing the plate is hazardous and may not completely solve the problem, plugs are often the best solution.
If performed with care and skill, the Bridge Saver repair is a guitar life saver. Just don't try this at home. You will ruin that prized GP Custom.
A note to you DIY'ers out there: Dan Erlewine's video tape shows him applying super glue to the string holes. Other resources suggest filling enlarged string holes with super glue and saw dust. The Bridge Saver repair using Brazilian Rosewood plugs is much superior to both of these techniques in terms of improved tone quality. I tried the super glue technique, followed by the Bridge Saver repair on the same guitar. The Bridge Saver technique is the clear winner. However, at this point, no one can guarantee how long Bridge Saver repairs will last. I think this is a stable repair, but who can tell what will happen in twenty or so years.