If you are recording a guitar, you probably ran into an issue with some weird sounds and overtunes heard in the recording. That is exactly what this little gadget is here to remove. After putting this on my ESP LTD EC-1000 I did not notice a difference - but after putting it on my Epiphone Les Paul Special, I could clearly hear the difference.
That's more a testament of how awesome ESP's are, but regardless, you will most likely not hear the difference in a live setting (unless you have super awesome in-ear monitors, ala Matt Heafy, where you can hear the most minute imperfections).
If you love recording your guitar and want to get rid of overtones even after playing the section perfectly, this should be a weapon of choice in your arsenal.
Bonus point: Personally, it also looks cool on a guitar.