Extremely good and powerful. I am using it as complimentary add-on for in-built bookmarks system and it has already considered many possible use cases like de-duplication, close stashed/saved tabs, highlight opened tabs, and it even updates order of bookmarks if the actual tabs are re-arranged before saving! I also recommend setting this extension page as homepage so all links are neatly organized and accessible. This wouldn't be possible without this add-on, anyone used to papaly will know exactly how useful this is. Also you can import links and file structure from copied list of bookmarks.