Unlike other iPod software to copy songs off the iPod, iPod.iTunes does real add-synchronization, even in two directions, if desired. The content source can be the iPod but also the iTunes library.

iPod.iTunes evaluates the source for content (songs, videos, podcasts and/or playlists) and only adds missing content seamlessly to the target, without duplicates, saving your time.

Unlike iTunes' own mirror-synchronization iPod.iTunes leaves your content intact, nothing will be deleted during synchronizations (add-synchronization).
iPod.iTunes can also transfer song dependent data like "My Rating", "Last Played", "Play Count", album artwork, etc...