This is one of the best things you can do for that new or used guitar. I’ve seen many new guitars that just don’t have level frets and fret out all over. I also have seen many used guitars with frets so out of level you can’t play clean notes anywhere but a few places. Over time the fret board changes dimensions, frets rise ever so slightly and as far as the strings are concerned it’s a roller coaster. A lot of people will live with it for a while, especially electric players because of the distortion they use. But those that do are missing a tremendous amount of tone and sustain. Acoustic players hear it in every note and can’t tolerate it.
Take a close look at your guitar. Turn it down and play cleanly up and down the neck. If you hear buzzing of loss of sustain, you could very well use a leveling and setup. If your guitar is fairly old you probably need it. The tone is so basic to a good performance. Don’t try to live without it.