From the NCBI site:
"Students performed a large number of ‘away’ rotations as ‘auditions’ in order to improve their chances in the match. For certain competitive specialties, virtually all students auditioned. Overall, students who did not audition were just as successful as or more successful than students who did audition."
To my understanding it could be detrimental to do an Audition Elective unless you are going into major specialties such as Dermatology. Saying that, many think that the Audition Elective is not a guarantee for a Match.