There is also Notebook from Circusponies. It used to be my fav app, but development has stalled and the iPad version was hands down terrible last time I checked.
Not the same as onenote but reasonably good as a journal app is also MacJournal. Good iPad app, but syncing was still via wifi last time I checked.
Like others, I have moved on to Evernote. I am not so blown away, cause it lacks formatting options and other stuff, but the integration across devices is top.