ipad productivity - noteshelf and iannotate pdf

A friend introduced several note taking apps for ipad - such as Noteshelf, iannotate pdf, penultimate. He recommended Noteshelf (only for ipad USD4.99)

Tested Noteshelf - http://iskandarsuhaili.blogspot.com/2011/12/sample-from-noteshelf-ipad-apps.html