They haven't implemented the killer feature yet... the ability to highlight and annotate documents, and share those highlights. For instance, you read a paper

They haven't implemented the killer feature yet... the ability to highlight and annotate documents, and share those highlights. For instance, you read a paper and find some portion interesting, I want see that portion and then if I need more info I can read the whole thing. Also, I want them to integrate with the university library system like google does so that I can get authenticated access to the documents.