It would be really great if you could mark the references in your library as ‘read’ or ‘unread’, perhaps as bolded entries just like in your email inbox. I am currently using the ‘Label’ field to write down which ones have been read, but this isn’t as visually striking.
On a parallel thought, the ability to change the colour of the text in the library listing of the references (not in the text of the document) could also prove quite useful for helping you to mark references, particularly if you have many groups.
Thanks!