New (actually returning) OD user here who hasn't tried Start10 yet. From what I understand, there doesn't seem to be any reason to install it if you prefer the Windows 10 style menu. It's strictly for those who want to replace it with a custom or legacy style menu. There's one thing I wish Start10 or some OD utility could do that would inspire me to install it immediately:
~ The ability to assign a single custom icon to tile group folders ~
Imagine how much cleaner the Start menu below would look if I could choose a single large icon for most or all of those tile folders—especially if the icons are from a uniformly styled collection. We should also be able to choose an icon from any app or at least choose one of the apps in that folder instead of all those tiny icons that make the entire menu look cluttered. Perhaps folders with a single icon could remain distinguishable from apps by adding square brackets around the name or something. In any case, it'll be obvious once you click on it.
Could features like this significantly expand interest in purchasing/using Start10? Well, I guarantee it would expand by at least 1.