Real paper for your iPad. It works! – Ink for iOS Review

Simple and easy to use with no "settings" to break your train of thought. Just a pen and paper. For $4.00 you can get four more colors. Cheaper than an analog pad of paper and pens, and great when you want to quickly jot something down or make a quick sketch and don't want to use a full-featured drawing app.
Review by BassmanBill on Ink for iOS.