I find its interface a little overwrought: your notes are kept in “pages,” which are nested into “sections,” which are then nested into multiple “notebooks” (and you can even have subpages nested within your pages). The extra layers of organization are the most infuriating things about OneNote. The second most infuriating thing is that it treats each page like a “canvas” where text is just one of many possible elements — which is great in theory, but in practice sometimes makes for a weird interface where you end up typing in an extraneous text box.
If you’re not annoyed to death by those interface issues, you’ll find OneNote to be fast, reliable, and powerful.
However, it is the nesting feature that allows me to have notebooks on the Bible, Biblical Theology, Systematic Theology, etc. with sections and pages that cover the books and chapters of the Bible or the loci of Systematic Theology and their doctrines. I’ve not found other note-taking apps to allow for this kind of organization.
The canvas feature is not quite as essential to my note-taking. But especially on work projects, I make use of it to organize material that I want to keep distinct, but still want to gather on a single page.