This is actually quite a clever innovation, since the biggest shortcoming of the other dance games (so I've heard) is that after a while, the music on the games gets kind of stale, no matter how catchy and clever it was when you first started playing the game. Each game comes with a lot of music, but you can only fit a finite amount of music on a game CD-ROM. So Vib-Ribbon bypasses that shortcoming by enlisting your own music collection. Reviews say that this leads to a lot of replayability.
Unfortunately, it is currently only available in Japan, and soon in Europe. Sony hasn't indicated that it has any plans to bring it to America. Please, Sony!