I switched from pinboard to diigo around 2 years ago. I love the "Annotate Page" functionality. I use it on all my bookmarks to quickly save the parts that I found useful or interesting. It is particularly useful when bookmarking HN/Reddit discussions, newsletters / link aggregations like High Scalability Newsletter. The hightlights are available when I open the page later so I know what I liked. Furthermore, the highlights show up when browsing the bookmarks on diigo, which makes it really great for research.