While many users simply use slides as a background for their own real time speech, MANY of us would like to create slide presentations with background music and/or offline narration. "And/or" means loading the music and voice on separate tracks. Along with adding MUSIC (it's a greatly anticpated feature - trust me) would be the ability to change slides on command, not an "in every" choice, such as change slides every 10 seconds or every 3 seconds. As said better in another post, set showing time for each slide independently. Repeat: These are greatly anticipated features.
Voice over would be an awesome feature especially for educators.