viewTunes is not meant as a replacement for iTunes. Instead it compliments iTunes ability to manage a great amount of information by offering a user interface that is focused on the music itself.
No need to maintain multiple music libraries: viewTunes uses your iTunes Music Library so you always have access thy your newest tracks. Any music added to iTunes is available to viewTunes when it is started.
Listen to all of your music! viewTunes is a QuickTime based music player, so in addition to all the popular music formats supported by QuickTime, you can even listen to music purchased at the iTunes Music Store.