Umm, I'd say the moments which rubbed me the wrong way are when Ron and Hermione fight in the first parts of the series. From what I remember, I was largely annoyed by how often they would argue over the smallest of things. Overall, I like them much better when they work together, so it's kind of why I tend to favour their moments in book 7 as opposed to their moments in the earlier books.

Then again, now that I'm older and understand that teenagers often argue because they're new at dealing with complex relationships, I might not find that Ron and Hermione's arguments as annoying if I watched and read all the books again. *shrugs* I guess I'll have to schedule a rewatch. :)