iPad: Noteshelf is a finely polished handwriting app with loads of features including 17 notebook templates, the ability to embed and annotate photos, over 450 icons, and automatic syncing to Dropbox and Evernote.
The templates fill most needs: in addition to ruled lines and graph "paper" you also have musical notation paper, shopping lists, baseball scores, day planners and personal journals. While using your fingertip works well, you'll probably want to eventually use a stylus to write with a finer tip. All of your saved notes go to an iBook-like library. The wrist protection features is also nice; when this is activated you can rest your wrist on the screen without worrying about creating unwanted lines as you write or draw.
At $5.49 the app is a bit spendy but worth it if you do a lot of handwriting on your iPad. The interface is gorgeous, it syncs with Dropbox and Evernote, and it allows a wide range of expression. Make sure to see all of the screenshots on the developer's page as well as the map screenshot at the iTunes Web Store link below to see the full capability if you're interested in the app before making your decision.