Moodle 2.x appears to have removed the "Reports" and "Participants" sections of the "Course Administration" menu. They seem to have been moved to sit under the course in the Navigation block.
This not only makes it difficult for users moving from 1.x to 2.x to find these reports, but also adds to the already rather lengthy Navigation block (in a large/complex course, just the course's section can get very long - adding course admin items such as these only makes it even longer) - and the consensus amongst people I've spoken to seems to be that Participants and Reports should be under Course Administration, as that's what they are. Essentially, there's a perfectly good "Course Administration" menu for course admin tools such as these, so they shouldn't really be cluttering up the Navigation block.
If there's a Good Reason for this change, please feel free to enlighten me - I've tried searching both the tracker and the forums, but didn't turn up anything at all relating to this change.