For me it's pretty much perfect - it syncs with all my devices, supports the iPad pencil, supports OCR and text searching in images, has native apps, and it's free.
One of the key things that kills it for me is that I really need my notetaking tool to be smart. I tag lines as "to-do", and my tool of choice can assemble an agenda of items i need to accomplish in a metadocument, even if they're spanned across multiple files.
OneNote, frustratingly, HAS a way to tag something as a Todo, but it's just decoration. There's no provision for showing you all the Todos in a document in a summarized view or whatever, or at least none I could find.
I'm willing to admit that my need here to comingle todo items and notes is perhaps idiosyncratic, but fortunately it's not TOO niche because it's basically the foundational idea of Orgmode.
(....and that's the story of how Ubermonkey became an emacs user.)