i've seen some comments on the Verge review ("a revelation. It’s very much the difference between a fine-tip pencil and a gigantic permanent marker") but not detailed comparison about how, for example, it is to annotate PDFs using one of the PDF annotation apps on the iPad vs. the 10.1? has anyone tried annotating PDFs on both? i'm a PhD student and looking at this as a possible solution for journal article reading and annotation. thanks.