It's a simple tool for someone like me who is not too good at using a knife to level cakes. I usually end up making it worse when I use a knife. This is fairly simple, set it to the same notch on either side and pull across. It's good for torting cakes too.
It's not big enough for every cake, and sometimes if I have a hard crust I need a knife to get it going initially, but still a good little tool.