On Windows it makes the Start menu fast and comfortable - instead of having some things slide in from one direction and others from another direction, the Start menu just appears instantly. I used to use Start10, but after disabling animation and deleting the tiles I don't need, I'm just as happy with the Windows native Start menu. I mostly just use the type-and-search rather than clicking on icons, so the less fanfare the Start menu presents, the better.
A couple of other settings I like in Windows 10 are also in the ease of access settings under the cursor and pointer section. I changed the cursor thickness to 3 for my high-DPI displays, and found a nice solid black mouse pointer there too - much easier to see than the default white one.
Whatever OS you are on, take a look through the accessibility settings. That is where they hide a lot of the good stuff.