Ah, sorry, I should have specified that I'm referring to the Android app. I've updated my comment accordingly. Not only is the interface a pain to work with, it has frequent syncing issues as well.

On the desktop, I'm forced to use the web client for OneNote and OneDrive, due to the lack of Linux support. I would definitely describe both as "clunky", though OneDrive is decidedly the worse offender of the two.