When I first installed the OneNote app on the iPad there wasn't much I could do with it because all my OneNote notebooks were OneNote 2007 format so I could access them (from a USB stick) on all machines (including the one running Office 2007).
OneNote for the iPad however required OneNote 2010 format so all I could do at the time was to create a single page OneNote 2010 format notebook in OneNote iPad itself and see how it looked.
But then I got the new portable and created a couple of OneNote 2010 notebooks (with genuine content) and, as discussed in an earlier post, stored them in SkyDrive.
Today I thought about seeing what if anything OneNote for the iPad would do with them. At first it seemed the answer was "nothing at all" because when I opened the OneNote app all I could see was that earlier single page test notebook.
So I clicked all the available menu line "buttons" looking for one that would let me specify "show me my SkyDrive content" and on clicking one of them for I think the second time, there were now three different SP 2010 notebooks listed - the local one and the two recently created SkyDrive ones.
In other word the app had gone automatically to SkyDrive; found the new two notebooks and added them to its listing of Notebooks.
No doubt there are some limitations in what OneNote content you can see / play on an iPad, but for my text plus images technical content taken mainly from web sources, it's fine.
Except that is for the fact that on the iPad you have to copy/paste URLs from the OneNote page into Safari. No double-clicking here I'm afraid.