There’s a new version of OneNote available (1.2) which introduces search, shared notebooks, and more customization options. OneNote app for iPhone will now also be available in 5 additional markets: Canada, the UK, Ireland, Australia, and New Zealand.
Microsoft OneNote for iPhone, iPod touch, and iPad on the iTunes App Store
For more details pl chk - OneNote Blog - OneNote Mobile for iPhone 1.2 delivers new features and is available in new markets

OneNote Mobile for iPhone is free for a limited time, so don't delay!