The Markbook allows you to view your students' marks in each nugget.  You can use this if you set a nugget to the whole class to identify misconceptions at a class level.  It can also be used to identify individual students or small groups of students who are struggling in a particular area.  By clicking on a cell, you can see a full breakdown of a student's attempt; including the time a student spent on the learning material and each question. You can also see where they answered correctly, incorrectly or if they skipped a question.