Not so much for the tidying part (though I did find that extremely helpful), but the whole idea of only keeping things in your life that "spark joy" (not an exact translation by the way - "spark excitement" or "spark meaning" are other ways I like to think about it) has had a profound impact on me.
I realized there were lots of things in my life (much more than just physical objects) that I had just sort of accumulated without thinking about what I really like or if something was good for me. I found the benefit of "practicing" this concept without mundane household objects allowed me to have a stronger sense of what I really enjoy in the more important aspects of my life.