After trying notability and Goodnotes, the best note taking app for me is Goodnotes. Although it is lacking some features such as the ability to add shapes, it is an extremely good note taking app that has been optimized for the iPad's retina display. The best feature in my opinion is the highlight tool. Instead of having a faint streak through the words you highlight, the app puts the highlight background to the text. This works on PDF files as well. There is a free version as well as a paid version so try it out yourself and see if it suits your needs when you get you new iPad.